Autism#Signs and symptoms

Before the DSM-5 (2013) and ICD-11 CDDR (2024){{Cite web |url=https://www.who.int/publications/i/item/9789240077263 |title=Clinical descriptions and diagnostic requirements for ICD-11 mental, behavioural and neurodevelopmental disorders (CDDR) |website=www.who.int |access-date=2025-01-23}} diagnostic manuals were adopted, autism was found under the diagnostic category pervasive developmental disorder. The previous system relied on a set of closely related and overlapping diagnoses such as Asperger syndrome and the syndrome formerly known as Kanner syndrome. This created unclear boundaries between the terms, so for the DSM-5 and CDDR, a spectrum approach was taken. The new system is also more restrictive, meaning fewer people qualify for diagnosis.{{cite web |url=https://www.parents.com/health/autism/what-happened-to-aspergers/ |title=Why Asperger's Syndrome is no longer listed in the DSM |website=parents.com |access-date=26 December 2022 |archive-date=26 December 2022 |archive-url=https://web.archive.org/web/20221226202800/https://www.parents.com/health/autism/what-happened-to-aspergers}}

The DSM-5 and CDDR use different categorization tools to define this spectrum. DSM-5 uses a "level" system, which ranks how in need of support the patient is. In this system, level 1 is the mildest form and level 3 the most severe.{{cite web |url=https://www.cdc.gov/ncbddd/autism/hcp-dsm.html |title=Diagnostic Criteria | Autism Spectrum Disorder (ASD) | NCBDDD | CDC |date=2 November 2022 |access-date=21 February 2021 |archive-date=16 August 2019 |archive-url=https://web.archive.org/web/20190816080840/https://www.cdc.gov/ncbddd/autism/hcp-dsm.html |url-status=live}} In contrast, the CDDR system has two separate axes, intellectual impairment and language impairment,{{cite web |url=https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/437815624 |title=ICD-11 for Mortality and Morbidity Statistics |access-date=6 April 2022 |archive-date=1 August 2018 |archive-url=https://archive.today/20180801205234/https://icd.who.int/browse11/l-m/en%23/http://id.who.int/icd/entity/294762853#/http://id.who.int/icd/entity/437815624 |url-status=live}} as these are seen as the most crucial factors.

Autism is currently defined as a highly variable neurodevelopmental disorder{{cite journal |vauthors=Geschwind DH |title=Autism: many genes, common pathways? |journal=Cell |volume=135 |issue=3 |pages=391–395 |date=October 2008 |pmid=18984147 |pmc=2756410 |doi=10.1016/j.cell.2008.10.016}} that is generally thought to cover a broad and deep spectrum, manifesting very differently from one person to another. Some have high support needs, may be nonspeaking, and experience developmental delays; this is more likely with other co-existing diagnoses. Others have relatively low support needs; they may have more typical speech-language and intellectual skills but atypical social/conversation skills, narrowly focused interests, and wordy, pedantic communication.{{cite journal |vauthors=Happé F |year=1999 |title=Understanding assets and deficits in autism: why success is more interesting than failure |url=http://www.thepsychologist.org.uk/archive/archive_home.cfm/volumeID_12-editionID_46-ArticleID_133-getfile_getPDF/thepsychologist/psy_11_99_p540-547_happe.pdf |journal=Psychologist |volume=12 |issue=11 |pages=540–547 |archive-url=https://web.archive.org/web/20120517162434/http://www.thepsychologist.org.uk/archive/archive_home.cfm/volumeID_12-editionID_46-ArticleID_133-getfile_getPDF/thepsychologist/psy_11_99_p540-547_happe.pdf |archive-date=17 May 2012}} They may still require significant support in some areas of their lives. The spectrum model should not be understood as a continuum running from mild to severe, but instead means that autism can present very differently in each person,{{cite journal |vauthors=Wing L |title=The autistic spectrum |language=English |journal=The Lancet |volume=350 |issue=9093 |pages=1761–1766 |date=December 1997 |pmid=9413479 |doi=10.1016/S0140-6736(97)09218-0 |s2cid=7165992}} with support needs depending on context and changing over time.{{cite web |title=Diagnostic criteria – a guide for all audiences |url=https://www.autism.org.uk/advice-and-guidance/topics/diagnosis/diagnostic-criteria/all-audiences |access-date=1 December 2022 |website=National Autistic Society |language=en |archive-date=21 September 2023 |archive-url=https://web.archive.org/web/20230921010739/https://www.autism.org.uk/advice-and-guidance/topics/diagnosis/diagnostic-criteria/all-audiences |url-status=live}}

While the DSM and ICD greatly influence each other, there are also differences. For example, Rett syndrome was included in autism spectrum disorder (ASD) in the DSM-5, but in the ICD-11 it was excluded and placed in the chapter on Developmental Anomalies. The ICD and the DSM change over time, and there has been collaborative work toward a convergence of the two since 1980 (when DSM-III was published and ICD-9 was current), including more rigorous biological assessment—in place of historical experience—and a simplification of the classification system.{{cite news |date=2009 |title=ICD vs. DSM |volume=40 |page=63 |newspaper=APA Monitor |publisher=American Psychological Association |number=9 |url=https://www.apa.org/monitor/2009/10/icd-dsm |access-date=22 October 2021 |archive-date=29 December 2022 |archive-url=https://web.archive.org/web/20221229093045/https://www.apa.org/monitor/2009/10/icd-dsm |url-status=live}}{{cite journal |vauthors=Mezzich JE |date=2002 |title=International surveys on the use of ICD-10 and related diagnostic systems |journal=Psychopathology |volume=35 |issue=2–3 |pages=72–75 |doi=10.1159/000065122 |pmid=12145487 |s2cid=35857872}}{{cite journal |vauthors=Goldberg D |date=January 2010 |title=The classification of mental disorder: a simpler system for DSM–V and ICD–11 |journal=Advances in Psychiatric Treatment |volume=16 |pages=14–19 |doi=10.1192/apt.bp.109.007120 |doi-access=free |number=1}}

As of 2023, empirical and theoretical research highlights how established ASD criteria may be ineffective descriptors of autism as a whole, encouraging alternative research approaches, such as going back to autism prototypes, exploring new causal models of autism, or developing transdiagnostic endophenotypes.{{cite journal |last1=Waterhouse |first1=Lynn |last2=Mottron |first2=Laurent |title=Editorial: Is autism a biological entity? |journal=Frontiers in Psychiatry |volume=14 |date=2 May 2023 |doi=10.3389/fpsyt.2023.1180981 |pmid=37200904 |pmc=10185896 |doi-access=free}} There are proposed alternatives to the current disorder-focused spectrum model that deconstruct autism into separate phenomena: (1) a non-pathological spectrum of behavioral traits in the population,{{cite journal |last1=Sarovic |first1=Darko |date=16 November 2021 |title=A Unifying Theory for Autism: The Pathogenetic Triad as a Theoretical Framework |journal=Frontiers in Psychiatry |volume=12 |doi=10.3389/fpsyt.2021.767075 |pmid=34867553 |pmc=8637925 |doi-access=free}}{{cite journal |last1=Chawner |first1=Samuel |date=2 September 2022 |title=Autism: A model of neurodevelopmental diversity informed by genomics |journal=Frontiers in Psychiatry |volume=13 |doi=10.3389/fpsyt.2022.981691 |pmid=36117659 |pmc=9479184 |doi-access=free}} (2) the effect of rare genetic mutations and environmental factors potentially leading to neurodevelopmental and psychological conditions, and (3) individual cognitive ability's role in compensating for neurodivergence.

The World Health Organization's International Classification of Diseases (11th revision), ICD-11, was released in June 2018 and came into full effect as of January 2022.{{cite web |url=https://www.who.int/news/item/18-06-2018-who-releases-new-international-classification-of-diseases-(icd-11) |title=WHO releases new International Classification of Diseases (ICD 11) |website=World Health Organization |type=Press Release |access-date=29 October 2021 |archive-date=25 December 2021 |archive-url=https://web.archive.org/web/20211225230744/https://www.who.int/news/item/18-06-2018-who-releases-new-international-classification-of-diseases-(icd-11) |url-status=live}}{{cite report |vauthors=Pickett D, Anderson RN |title=Status on ICD-11: The WHO Launch |url=https://ncvhs.hhs.gov/wp-content/uploads/2018/08/ICD-11_WHO-v_7-17-2018.pdf |date=18 July 2018 |publisher=CDC/NCHS |access-date=22 October 2021 |archive-date=15 March 2023 |archive-url=https://web.archive.org/web/20230315022814/https://ncvhs.hhs.gov/wp-content/uploads/2018/08/ICD-11_WHO-v_7-17-2018.pdf |url-status=live}} It describes ASD as follows:{{sfn|ICD-11}}

{{Blockquote|text=Autism spectrum disorder is characterised by persistent deficits in the ability to initiate and to sustain reciprocal social interaction and social communication, and by a range of restricted, repetitive, and inflexible patterns of behaviour, interests or activities that are clearly atypical or excessive for the individual's age and sociocultural context. The onset of the disorder occurs during the developmental period, typically in early childhood, but symptoms may not become fully manifest until later, when social demands exceed limited capacities. Deficits are sufficiently severe to cause impairment in personal, family, social, educational, occupational or other important areas of functioning and are usually a pervasive feature of the individual's functioning observable in all settings, although they may vary according to social, educational, or other context. Individuals along the spectrum exhibit a full range of intellectual functioning and language abilities.|title=ICD-11|source=chapter 6, section A02}}

ICD-11 was produced by professionals from 55 countries out of the 90 involved and is the most widely used reference worldwide.

The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR), released in 2022, is the current version of the DSM. It is the predominant mental health diagnostic system used in the United States and Canada, and is often used in Anglophone countries.

Its fifth edition, DSM-5, released in May 2013, was the first to define ASD as a single diagnosis,{{cite Q|Q3064664}} which is still the case in the DSM-5-TR.{{sfn|DSM-5-TR}} ASD encompasses previous diagnoses, including the four traditional diagnoses of autism—classic autism, Asperger syndrome, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS)—and the range of diagnoses that included the word "autism".{{sfn|DSM-5-TR|loc="Autism spectrum disorder encompasses disorders previously referred to as early infantile autism, childhood autism, Kanner's autism, high-functioning autism, atypical autism, pervasive developmental disorder not otherwise specified, childhood disintegrative disorder, and Asperger's disorder"}} Rather than distinguishing among these diagnoses, the DSM-5 and DSM-5-TR adopt a dimensional approach with one diagnostic category for disorders that fall under the autism spectrum umbrella. Within that category, the DSM-5 and the DSM include a framework that differentiates each person by dimensions of symptom severity, as well as by associated features (i.e., the presence of other conditions or factors that likely contribute to the symptoms, other neurodevelopmental or mental conditions, intellectual disability, or language impairment).{{sfn|DSM-5-TR}} The symptom domains are (a) social communication and (b) restricted, repetitive behaviors, and there is the option of specifying a separate severity—the negative effect of the symptoms on the person—for each domain, rather than just overall severity.{{sfn|DSM-5-TR|loc="It may be helpful to note level of support needed for each of the two core psychopathological domains in Table 2 (e.g., 'requiring very substantial support for deficits in social communication and requiring substantial support for restricted, repetitive behaviors')"}} Before the DSM-5, the DSM separated social deficits and communication deficits into two domains.{{cite journal |vauthors=Kulage KM, Smaldone AM, Cohn EG |title=How will DSM-5 affect autism diagnosis? A systematic literature review and meta-analysis |journal=Journal of Autism and Developmental Disorders |volume=44 |issue=8 |pages=1918–1932 |date=August 2014 |pmid=24531932 |doi=10.1007/s10803-014-2065-2 |s2cid=18865395}} Further, the DSM-5 changed to an onset age in the early developmental period, with a note that symptoms may manifest later when social demands exceed capabilities, rather than the previous, more restricted three years of age.{{cite web |title=DSM-5 Diagnostic Criteria |url=https://iacc.hhs.gov/about-iacc/subcommittees/resources/dsm5-diagnostic-criteria.shtml#autism-spectrum-disorder |publisher=U.S. Department of Health & Human Services Interagency Autism Coordinating Committee |access-date=17 May 2017 |archive-date=11 February 2017 |archive-url=https://web.archive.org/web/20170211004905/https://iacc.hhs.gov/about-iacc/subcommittees/resources/dsm5-diagnostic-criteria.shtml#autism-spectrum-disorder |url-status=live}} These changes remain in the DSM-5-TR.{{sfn|DSM-5-TR}}

{{Expand section|date=April 2025}}

A person for whom there is reasonable expectation of autism can undergo assessment to determine whether a formal diagnosis of autism is appropriate to describe the difficulties they are experiencing. Assessment should take into account both the person's reported and directly observed behavior.{{cite journal |vauthors=Baird G, Cass H, Slonims V |date=August 2003 |title=Diagnosis of autism |journal=BMJ |volume=327 |issue=7413 |pages=488–493 |doi=10.1136/bmj.327.7413.488 |pmc=188387 |pmid=12946972}} There are no known biomarkers for autism that allow for a conclusive diagnosis.{{Cite journal |last1=Lord |first1=Catherine |author-link=Catherine Lord (psychologist) |last2=Charman |first2=Tony |last3=Havdahl |first3=Alexandra |last4=Carbone |first4=Paul |last5=Anagnostou |first5=Evdokia |last6=Boyd |first6=Brian |last7=Carr |first7=Themba |last8=de Vries |first8=Petrus J |last9=Dissanayake |first9=Cheryl |author-link9=Cheryl Dissanayake |last10=Divan |first10=Gauri |last11=Freitag |first11=Christine M |last12=Gotelli |first12=Marina M |last13=Kasari |first13=Connie |last14=Knapp |first14=Martin |last15=Mundy |first15=Peter |date=2022 |title=The Lancet Commission on the future of care and clinical research in autism |journal=The Lancet |language=en |volume=399 |issue=10321 |pages=271–334 |doi=10.1016/S0140-6736(21)01541-5 |pmid=34883054 |s2cid=244917920|hdl=11250/2975811 |hdl-access=free }} In most cases, diagnostic criteria are applied from the World Health Organization's ICD-10 or ICD-11, or the American Psychiatric Association's DSM-5. One commonly used assessment tool is the Autism Diagnostic Observation Schedule, which can be used at any age. In children, assessment tools such as these are used in combination with other information, such as parent and teacher reports.{{Cite web |title=Autism diagnostic observation schedule (ADOS) assessment |url=https://bedslutonchildrenshealth.nhs.uk/neurodiversity-support/neurodevelopmental-assessment-and-diagnosis-process/autism-diagnostic-observation-schedule-ados-assessment/ |access-date=2025-04-23 |website=bedslutonchildrenshealth.nhs.uk |language=en-GB}}

According to the DSM-5-TR (2022), to receive a diagnosis of autism spectrum disorder, one must present with "persistent deficits in social communication and social interaction" and "restricted, repetitive patterns of behavior, interests, or activities".{{Cite book |title=Diagnostic and statistical manual of mental disorders : DSM-5-TR |publisher=American Psychiatric Association Publishing |year=2022 |isbn=978-0-89042-575-6 |edition=Fifth edition, text revision. |location=Washington, DC |chapter=Section 2: Neurodevelopmental Disorders |type=Print}} These behaviors must begin in early childhood and affect one's ability to perform everyday tasks. Furthermore, the symptoms must not be fully explainable by intellectual disability or global developmental delay.

{{Cleanup section|reason=Bulleted list not appropriate|date=April 2025}}

For many autistic people, characteristics first appear during infancy or childhood and follow a steady course without remission (different developmental timelines are described in more detail below).{{cite web |year=2007 |title=F84. Pervasive developmental disorders |url=http://apps.who.int/classifications/apps/icd/icd10online/?gf80.htm+f84 |archive-url=https://web.archive.org/web/20130421042448/http://apps.who.int/classifications/apps/icd/icd10online/?gf80.htm%20f84 |archive-date=21 April 2013 |access-date=10 October 2009 |website=ICD-10: International Statistical Classification of Diseases and Related Health Problems: Tenth Revision |publisher=World Health Organization}} Autistic people may be significantly disabled in some respects but average, or even superior, in others.{{cite book |vauthors=Loukusa S |title=Handbook of Pragmatic Language Disorders |veditors=Cummings L |date=2021 |publisher=Springer |location=Cham, Switzerland |isbn=978-3-030-74984-2 |pages=45–78 |doi=10.1007/978-3-030-74985-9_3 |chapter=Autism Spectrum Disorder |s2cid=239160368 |oclc=1269056169}}{{cite book |title=Biopsychology |vauthors=Pinel JP |publisher=Pearson |year=2011 |isbn=978-0-205-03099-6 |edition=8th |location=Boston, Massachusetts |page=235 |oclc=1085798897}}{{cite book |title=Autism Spectrum Disorders |date=2018 |publisher=American Psychiatric Association |chapter=Cognitive Assessment |doi=10.1176/appi.books.9781615371921 |isbn=978-1-61537-192-1 |veditors=Hollander E, Hagerman R, Fein D}}

Clinicians consider assessment for ASD when a patient shows regular difficulty in social interaction or communication, restricted or repetitive behaviors (often called "stimming"), and resistance to changes or restricted interests.

These features are typically assessed with the following, when appropriate:

• Difficulties in obtaining or sustaining employment or education
• Difficulties in initiating or sustaining social relationships
• Connections with mental health or learning disability services
• A history of neurodevelopmental conditions (including learning disabilities and ADHD) or mental health conditions{{citation |title=Autism spectrum disorder in adults: diagnosis and management |date=14 June 2021 |url=https://www.nice.org.uk/guidance/cg142 |publisher=NICE |id=CG142 |access-date=24 October 2021 |archive-date=2 September 2023 |archive-url=https://web.archive.org/web/20230902193040/https://www.nice.org.uk/guidance/cg142 |url-status=live}}{{cite web |url=https://www.canada.ca/en/public-health/services/diseases/autism-spectrum-disorder-asd/about-autism-spectrum-disorder-asd.html |title=About autism spectrum disorder (ASD) |website=Government of Canada |language=en |date=18 January 2016 |access-date=4 November 2021 |archive-date=26 March 2023 |archive-url=https://web.archive.org/web/20230326225043/https://www.canada.ca/en/public-health/services/diseases/autism-spectrum-disorder-asd/about-autism-spectrum-disorder-asd.html |url-status=live}}

There are many signs associated with autism; the presentation varies widely. Common signs and characteristics include:{{cite web |url=https://www.canada.ca/en/public-health/services/diseases/autism-spectrum-disorder-asd/signs-symptoms-autism-spectrum-disorder-asd.html |title=What are the signs and symptoms of ASD? |website=Government of Canada |language=en |date=18 January 2016 |access-date=4 November 2021 |archive-date=1 June 2023 |archive-url=https://web.archive.org/web/20230601202634/https://www.canada.ca/en/public-health/services/diseases/autism-spectrum-disorder-asd/signs-symptoms-autism-spectrum-disorder-asd.html |url-status=live}}{{cite web |author= |date=25 March 2020 |title=What is Autism Spectrum Disorder? |url=https://www.cdc.gov/ncbddd/autism/facts.html |url-status=dead |archive-url=https://web.archive.org/web/20230921231100/https://www.cdc.gov/ncbddd/autism/facts.html |archive-date=21 September 2023 |access-date=24 October 2021 |website=Centers for Disease Control and Prevention}}

• Less eye contact
• Little or no babbling as an infant
• Not showing interest in indicated objects
• Delayed language skills (e.g., having a smaller vocabulary than peers or difficulty expressing themselves in words)
• Less interest in other children or caretakers, possibly with more interest in objects
• Difficulty playing reciprocal games (e.g., peek-a-boo)
• Hyper- or hypo-sensitivity to or unusual response to the smell, texture, sound, taste, or appearance of things
• Resistance to changes in routine
• Repetitive, limited, or otherwise unusual usage of toys (e.g., lining up toys)
• Repetition of words or phrases, including echolalia
• Repetitive motions or movements, including stimming

File:Temple Grandin at TED.jpg published Emergence: Labeled Autistic, describing her life experiences as an autistic person.]]

According to the medical model, autistic people experience social communications impairments. Until 2013, difficulties in social function and communication were considered two separate domains.{{cite journal |vauthors=Frye RE |title=Social Skills Deficits in Autism Spectrum Disorder: Potential Biological Origins and Progress in Developing Therapeutic Agents |journal=CNS Drugs |volume=32 |issue=8 |pages=713–734 |date=August 2018 |pmid=30105528 |doi=10.1007/s40263-018-0556-y |pmc=6105175}} The current social communication domain criteria for autism diagnosis require people to have difficulties across three social skills: social-emotional reciprocity, nonverbal communication, and developing and sustaining relationships.{{sfn|DSM-5-TR}}

A deficit-based view predicts that autistic–autistic interaction would be less effective than autistic–non-autistic interactions or even non-functional.{{Secondary source needed|date=April 2025}} But recent research has found that autistic–autistic interactions are as effective in information transfer as interactions between non-autistics are, and that communication breaks down only between autistics and non-autistics.{{cite journal |last=Crompton |first=Catherine J |date=20 May 2020 |title=Autistic peer-to-peer information transfer is highly effective |journal=Autism |language=en |volume=24 |issue=7 |pages=1704–1712 |doi=10.1177/1362361320919286 |pmid=32431157 |pmc=7545656}}{{Secondary source needed|date=April 2025}}{{cite journal |last1=Heasman |first1=Brett |last2=Alex |first2=Gillespie |title=Neurodivergent intersubjectivity: Distinctive features of how autistic people create shared understanding |url=https://eprints.lse.ac.uk/90098/1/Heasman_Neurodivergent-intersubjectivity_Published.pdf |journal=Autism |date=2019 |language=en |volume=23 |issue=4 |pages=910–921 |doi=10.1177/1362361318785172 |pmid=30073872 |pmc=6512057 |access-date=22 November 2023 |archive-date=16 November 2023 |archive-url=https://web.archive.org/web/20231116225321/https://eprints.lse.ac.uk/90098/1/Heasman_Neurodivergent-intersubjectivity_Published.pdf |url-status=live }}{{Secondary source needed|date=April 2025}} Also contrary to social cognitive deficit interpretations, research in 2019 recorded similar social cognitive performances in autistic and non-autistic adults, with both of them rating autistic individuals less favorably than non-autistic individuals; however, autistic individuals showed more interest in engaging with autistic people than non-autistic people did, and learning of a person's autism diagnosis did not influence their interest level.{{cite journal |first1=Kilee M. |last1=DeBrabander |first2=Kerrianne E. |last2=Morrison |first3=Desiree R. |last3=Jones |first4=Daniel J. |last4=Faso |first5=Mike |last5=Chmielewski |first6=Noah J. |last6=Sasson |date=13 December 2019 |title=Do First Impressions of Autistic Adults Differ Between Autistic and Nonautistic Observers? |journal=Autism in Adulthood |language=en |volume=1 |issue=4 |pages=250–257 |doi=10.1089/aut.2019.0018 |pmid=36601322 |pmc=8992824}}{{Secondary source needed|date=April 2025}}

Thus there has been a recent shift to acknowledge that autistic people may simply respond and behave differently than non-autistic people. So far, research has identified two unconventional features by which autistic people create shared understanding (intersubjectivity): "a generous assumption of common ground that, when understood, led to rapid rapport, and, when not understood, resulted in potentially disruptive utterances; and a low demand for coordination that ameliorated many challenges associated with disruptive turns." Autistic interests, and thus conversational topics, seem to be largely driven by an intense interest in specific topics (monotropism).{{cite journal |first1=Rachel |last1=Grove |first2=Rosa A |last2=Hoekstra |first3=Marlies |last3=Wierda |first4=Sander |last4=Begeer |date=20 May 2020 |title=Special interests and subjective wellbeing in autistic adults |journal=Autism Research |language=en |volume=11 |issue=5 |pages=766–775 |doi=10.1002/aur.1931 |pmid=29427546 |hdl=1871.1/d5c70844-3d23-4e71-8c5d-82533196b003 |s2cid=205456773 |url=https://research.vu.nl/en/publications/d5c70844-3d23-4e71-8c5d-82533196b003 |hdl-access=free}}{{cite journal |first1=Dinah |last1=Murray |first2=Mike |last2=Lesser |first3=Wendy |last3=Lawson |date=May 2005 |title=Attention, monotropism and the diagnostic criteria for autism |journal=Autism Research |language=en |volume=9 |issue=2 |pages=139–156 |doi=10.1177/1362361305051398 |pmid=15857859 |s2cid=6476917 |doi-access=free}}

Historically, autistic children were said to be delayed in developing a theory of mind, and the empathizing–systemizing theory has argued that while autistic people have compassion (affective empathy) for others with similar presentation of autistic features, they have limited, though not necessarily absent, cognitive empathy.{{cite journal |last1=Baron-Cohen |first1=Simon |last2=Knickmeyer |first2=Rebecca C. |last3=Belmonte |first3=Matthew K. |author1-link=Simon Baron-Cohen |title=Sex differences in the brain: implications for explaining autism |journal=Science |volume=310 |issue=5749 |pages=819–823 |doi = 10.1126/science.1115455 |pmid=16272115 |date=4 November 2005 |bibcode=2005Sci...310..819B |s2cid=44330420 |url=http://docs.autismresearchcentre.com/papers/2005_BC_etal_Science.pdf |access-date=10 September 2023 |archive-date=17 May 2017 |archive-url=https://web.archive.org/web/20170517064851/http://docs.autismresearchcentre.com/papers/2005_BC_etal_Science.pdf |url-status=live}} This may present as social naïvety,{{cite book |vauthors=Klin A, Volkmar FR, Sparrow SS |date=2000 |chapter=Introduction |veditors=Klin A, Volkmar FR, Sparrow SS |title=Asperger syndrome |location=New York |publisher=Guilford Press |pages=1–24 |isbn=1-57230-534-7}} lower than average intuitive perception of the utility or meaning of body language, social reciprocity,{{cite journal |last=Gernsbacher |first=Morton Ann |date=6 August 2017 |title=Editorial Perspective: The use of person-first language in scholarly writing may accentuate stigma |journal=Journal of Child Psychology and Psychiatry |language=en |volume=58 |issue=7 |pages=859–861 |doi=10.1111/jcpp.12706 |pmc=5545113 |pmid=28621486}} or social expectations, including the habitus, social cues, and some aspects of sarcasm,{{cite web |title=DSM-5 Full Text Online |url=http://repository.poltekkes-kaltim.ac.id/657/1/Diagnostic%20and%20statistical%20manual%20of%20mental%20disorders%20_%20DSM-5%20(%20PDFDrive.com%20).pdf |url-status=live |access-date=10 January 2022 |website=Repository Poltekkes Kaltim |archive-url=https://archive.today/20220108082216/http://repository.poltekkes-kaltim.ac.id/657/1/Diagnostic%20and%20statistical%20manual%20of%20mental%20disorders%20_%20DSM-5%20(%20PDFDrive.com%20).pdf |archive-date=8 January 2022}} which to some degree may also be due to co-occurring alexithymia.{{cite book |vauthors=Hogeveen J, Grafman J |title=Disorders of Emotion in Neurologic Disease |chapter=Alexithymia |series=Handbook of Clinical Neurology |volume=183 |pages=47–62 |date=2021 |pmid=34389125 |pmc=8456171 |doi=10.1016/b978-0-12-822290-4.00004-9 |publisher=Elsevier |isbn=978-0-12-822290-4}} But recent research has increasingly questioned these findings, as the "double empathy problem" theory (2012) argues that there is a lack of mutual understanding and empathy between both non-autistic persons and autistic individuals.{{cite journal |last=Milton |first=Damian E. M. |date=October 2012 |title=On the ontological status of autism: the 'double empathy problem' |url=http://www.tandfonline.com/doi/abs/10.1080/09687599.2012.710008 |journal=Disability & Society |language=en |volume=27 |issue=6 |pages=883–887 |doi=10.1080/09687599.2012.710008 |issn=0968-7599 |s2cid=54047060 |access-date=22 November 2023 |archive-date=8 March 2023 |archive-url=https://web.archive.org/web/20230308062210/https://www.tandfonline.com/doi/abs/10.1080/09687599.2012.710008 |url-status=live }}{{cite journal |last1=Milton |first1=Damian |last2=Gurbuz |first2=Emine |last3=López |first3=Beatriz |date=November 2022 |title=The 'double empathy problem': Ten years on |url=http://journals.sagepub.com/doi/10.1177/13623613221129123 |journal=Autism |language=en |volume=26 |issue=8 |pages=1901–1903 |doi=10.1177/13623613221129123 |pmid=36263746 |s2cid=253020669 |issn=1362-3613 |access-date=25 February 2023 |archive-date=25 February 2023 |archive-url=https://web.archive.org/web/20230225135833/https://journals.sagepub.com/doi/10.1177/13623613221129123 |url-status=live}}{{cite journal |title=Double Empathy: Why Autistic People Are Often Misunderstood |year=2021 |language=en |doi=10.3389/frym.2021.554875|doi-access=free |last1=Crompton |first1=Catherine J. |last2=Debrabander |first2=Kilee |last3=Heasman |first3=Brett |last4=Milton |first4=Damian |last5=Sasson |first5=Noah J. |journal=Frontiers for Young Minds |volume=9|hdl=20.500.11820/94ee032a-6103-470a-bc06-08337dd6b512 |hdl-access=free }}{{cite journal |last1=Sasson |first1=Noah J. |last2=Faso |first2=Daniel J. |last3=Nugent |first3=Jack |last4=Lovell |first4=Sarah |last5=Kennedy |first5=Daniel P. |last6=Grossman |first6=Ruth B. |date=1 February 2017 |title=Neurotypical Peers are Less Willing to Interact with Those with Autism based on Thin Slice Judgments |journal=Scientific Reports |language=en |volume=7 |issue=1 |page=40700 |bibcode=2017NatSR...740700S |doi=10.1038/srep40700 |issn=2045-2322 |pmc=5286449 |pmid=28145411}}{{cite journal |vauthors=Hamilton AF |title=Goals, intentions and mental states: challenges for theories of autism |journal=Journal of Child Psychology and Psychiatry |volume=50 |issue=8 |pages=881–92 |year=2009 |pmid=19508497 |doi=10.1111/j.1469-7610.2009.02098.x |citeseerx=10.1.1.621.6275}}

Differences in verbal communication begin to be noticeable in childhood, as many autistic children develop language skills at an uneven pace. Verbal communication may be delayed or never developed (non-speaking autism), while reading ability may be present before school age (hyperlexia). Less joint attention seems to distinguish autistic from non-autistic infants.{{cite journal |vauthors=Johnson CP, Myers SM |date=November 2007 |title=Identification and evaluation of children with autism spectrum disorders |journal=Pediatrics |volume=120 |issue=5 |pages=1183–1215 |doi=10.1542/peds.2007-2361 |pmid=17967920 |doi-access=free}} Infants may show delayed onset of babbling, unusual gestures, diminished responsiveness, and vocal patterns that are not synchronized with the caregiver. In their second and third years, autistic children may have less frequent and less diverse babbling, consonants, words, and word combinations, and their gestures may be less often integrated with words. Autistic children are less likely to make requests or share experiences and more likely to simply repeat others' words (echolalia).{{cite journal |vauthors=Tager-Flusberg H, Caronna E |date=June 2007 |title=Language disorders: autism and other pervasive developmental disorders |journal=Pediatric Clinics of North America |volume=54 |issue=3 |pages=469–81, vi |doi=10.1016/j.pcl.2007.02.011 |pmid=17543905 |s2cid=13615727}} The CDC estimated in 2015 that around 40% of autistic children do not speak at all.{{cite web |url=https://www.cdc.gov/ncbddd/autism/signs.html |title=Signs & Symptoms: Autism Spectrum Disorder |date=26 February 2015 |author=National Center on Birth Defects and Developmental Disabilities |website=Centers for Disease Control and Prevention |archive-url=https://web.archive.org/web/20150310030922/https://www.cdc.gov/ncbddd/autism/signs.html |archive-date=10 March 2015}} (Also available in Spanish.) Autistic adults' verbal communication skills largely depend on when and how well speech is acquired during childhood.{{cite journal |first1=Vanessa H. |last1=Bal |first2=So-Hyun |last2=Kim |first3=Megan |last3=Fok |first4=Catherine |last4=Lord |date=12 August 2018 |title=Autism Spectrum Disorder symptoms from 2 to 19: Implications for diagnosing adolescents and young adults |journal=Autism Research |language=en |volume=12 |issue=1 |pages=89–99 |doi=10.1002/aur.2004 |pmc=6600818 |pmid=30101492}}

Autistic people display atypical nonverbal behaviors or show differences in nonverbal communication. They may make infrequent eye contact, even when called by name, or avoid it altogether. This may be due to the high amount of sensory input received when making eye contact.{{Cite journal |last1=Trevisan |first1=Dominic A. |last2=Roberts |first2=Nicole |last3=Lin |first3=Cathy |last4=Birmingham |first4=Elina |date=28 November 2017 |title=How do adults and teens with self-declared Autism Spectrum Disorder experience eye contact? A qualitative analysis of first-hand accounts |journal=PLOS ONE |language=en |volume=12 |issue=11 |pages=e0188446 |doi=10.1371/journal.pone.0188446 |doi-access=free |pmid=29182643 |pmc=5705114 |bibcode=2017PLoSO..1288446T |issn=1932-6203}} Autistic people often recognize fewer emotions and their meaning from others' facial expressions, and may not respond with facial expressions expected by their non-autistic peers.{{cite web |title=Autism: Overview |url=https://www.asha.org/Practice-Portal/Clinical-Topics/Autism/ |publisher=American Speech-Language-Hearing Association |access-date=17 December 2017 |archive-date=23 April 2019 |archive-url=https://web.archive.org/web/20190423134030/https://www.asha.org/Practice-Portal/Clinical-Topics/Autism/ |url-status=live}}{{cite web |date=18 August 2015 |title=Autism Spectrum Disorder: Communication Problems in Children |url=https://www.nidcd.nih.gov/health/autism-spectrum-disorder-communication-problems-children |access-date=17 December 2017 |website=NIDCD |archive-date=22 December 2017 |archive-url=https://web.archive.org/web/20171222090623/https://www.nidcd.nih.gov/health/autism-spectrum-disorder-communication-problems-children |url-status=live}} Temple Grandin, an autistic woman involved in autism activism, described her inability to understand neurotypicals' social communication as leaving her feeling "like an anthropologist on Mars".{{cite news |last1=Cohen |first1=David |last2=Grandin |first2=Temple |author2-link=Temple Grandin |title=Temple Grandin: 'I'm an anthropologist from Mars' |url=https://www.theguardian.com/education/2005/oct/25/highereducationprofile.academicexperts |access-date=6 July 2022 |work=The Guardian |issn=0261-3077 |eissn=1756-3224 |oclc=60623878 |location=Kings Place, London |publisher=Scott Trust |date=25 October 2005 |archive-url=https://web.archive.org/web/20131109145205/https://www.theguardian.com/education/2005/oct/25/highereducationprofile.academicexperts |archive-date=9 November 2013}} Autistic people struggle to understand the social context and subtext of neurotypical conversational or printed situations, and form different conclusions about the content.{{cite web |title=Social communication and language characteristics associated with high-functioning, verbal children and adults with autism spectrum disorder |url=https://www.iidc.indiana.edu/pages/Social-Communication-and-Language-Characteristics-Associated-with-High-Functioning-Verbal-Children-and-Adults-with-ASD |url-status=live |archive-url=https://web.archive.org/web/20181214181341/https://www.iidc.indiana.edu/pages/Social-Communication-and-Language-Characteristics-Associated-with-High-Functioning-Verbal-Children-and-Adults-with-ASD |archive-date=14 December 2018 |access-date=17 December 2017 |publisher=Indiana Resource Center for Autism |vauthors=Vicker B}} Autistic people may not control the volume of their voice in different social settings. At least half of autistic children have atypical prosody.{{cite journal |vauthors=Fusaroli R, Lambrechts A, Bang D, Bowler DM, Gaigg SB |date=March 2017 |title=Is voice a marker for Autism spectrum disorder? A systematic review and meta-analysis |url=https://pure.au.dk/ws/files/101709535/046565.full.pdf |journal=Autism Research |volume=10 |issue=3 |pages=384–407 |doi=10.1002/aur.1678 |pmid=27501063 |s2cid=13772771 |access-date=27 March 2020 |archive-date=20 March 2021 |archive-url=https://web.archive.org/web/20210320203509/https://pure.au.dk/ws/files/101709535/046565.full.pdf |url-status=live}}

What may look like self-involvement or indifference to non-autistic people stems from autistic differences in recognizing other people's personalities, perspectives, and interests.{{cite book |url=https://archive.org/details/understandingwor00laws_352 |title=Understanding and Working With the Spectrum of Autism: An Insider's View |vauthors=Lawson W |publisher=Jessica Kingsley Publishers |year=2001 |isbn=978-1-85302-971-4 |location=London UK, & Philadelphia PA |pages=[https://archive.org/details/understandingwor00laws_352/page/n33 33] |url-access=limited}} Most published research focuses on the interpersonal relationship difficulties between autistic people and their non-autistic counterparts and how to solve them through teaching neurotypical social skills, but newer research has also evaluated what autistic people want from friendships, such as a sense of belonging and benefits to mental health.{{cite journal |last1=Finke |first1=Erinn |date=16 May 2022 |title=The Kind of Friend I Think I Am: Perceptions of Autistic and Non‑autistic Young Adults |journal=Journal of Autism and Developmental Disorders |language=en |volume=53 |issue=8 |pages=3047–3064 |doi=10.1007/s10803-022-05573-4 |pmid=35570241 |s2cid=248812844 |url=https://www.researchgate.net/publication/360622541 |access-date=23 November 2023 |archive-date=6 March 2024 |archive-url=https://web.archive.org/web/20240306230604/https://www.researchgate.net/publication/360622541_The_Kind_of_Friend_I_Think_I_Am_Perceptions_of_Autistic_and_Non-autistic_Young_Adults |url-status=live }}{{cite journal |last1=O'Connor |first1=Rachel A G |first2=Neeltje |last2=van den Bedem |first3=Els M A |last3=Blijd-Hoogewys |first4=Lex |last4=Stockmann |first5=Carolien |last5=Rieffe |title=Friendship quality among autistic and non-autistic (pre-) adolescents: Protective or risk factor for mental health? |journal=Autism |date=22 January 2022 |language=en |volume=26 |issue=8 |pages=2041–2051 |doi=10.1177/13623613211073448 |pmid=35068188 |pmc=9597130}} Children on the autism spectrum are more frequently involved in bullying situations than their non-autistic peers, and predominantly experience bullying as victims rather than perpetrators or victim-perpetrators, especially after controlling for co-occurring psychopathology.{{cite journal |first1=Eeske |last1=van Roekel |first2=Ron H. J. |last2=Scholte |first3=Robert |last3=Didden |date=2010 |title=Bullying Among Adolescents With Autism Spectrum Disorders: Prevalence and Perception |journal=Journal of Autism and Developmental Disorders |volume=40 |issue=1 |pages=63–73 |doi=10.1016/j.pcl.2007.02.011 |pmid=17543905 |s2cid=13615727 |doi-access=free|pmc=2809311 }} Prioritizing dependability and intimacy in friendships during adolescence, coupled with lower friendship quantity and quality, often leads to increased loneliness in autistic people.{{cite journal |last1=O'Connor |first1=Rachel A G |first2=Neeltje |last2=van den Bedem |first3=Els M A |last3=Blijd-Hoogewys |first4=Lex |last4=Stockmann |first5=Carolien |last5=Rieffe |title=Sex differences in friendships and loneliness in autistic and non-autistic children across development |journal=Molecular Autism |date=November 2022 |language=en |volume=4 |issue=9 |page=9 |doi=10.1186/s13229-023-00542-9 |pmid=36829214 |pmc=9960478 |doi-access=free}} As they progress through life, autistic people observe and form models of social patterns, and develop coping mechanisms, some of which are referred to as "masking".{{cite journal |last1=Pearson |first1=Amy |last2=Rose |first2=Kieran |date=1 March 2021 |title=A Conceptual Analysis of Autistic Masking: Understanding the Narrative of Stigma and the Illusion of Choice |journal=Autism in Adulthood |volume=3 |issue=1 |pages=52–60 |doi=10.1089/aut.2020.0043 |issn=2573-9581 |pmc=8992880 |pmid=36601266}}{{cite journal |last1=Petrolini |first1=Valentina |last2=Rodríguez-Armendariz |first2=Ekaine |last3=Vicente |first3=Agustín |date=2023 |title=Autistic camouflaging across the spectrum |journal=New Ideas in Psychology |language=en |volume=68 |page=100992 |doi=10.1016/j.newideapsych.2022.100992 |hdl=10810/59712 |s2cid=253316582 |doi-access=free|hdl-access=free }}

File:Autistic-sweetiepie-boy-with-ducksinarow.jpg

Autism includes a wide variety of characteristics. Some of these include behavioral characteristics, which widely range from slow development of social and learning skills to difficulties creating connections with other people. Autistic people may experience these challenges with forming connections due to anxiety or depression, which they are more likely to experience, and may respond by isolating themselves.{{cite web |title=Engaging people on the autism spectrum |date=7 October 2013 |publisher=Autism Spectrum Australia |url=https://www.autismspectrum.org.au/about-aspect/diversity-inclusion/engaging-people-on-the-autism-spectrum |archive-url=https://web.archive.org/web/20200319233547/https://www.autismspectrum.org.au/about-aspect/diversity-inclusion/engaging-people-on-the-autism-spectrum |archive-date=19 March 2020 }}{{Cite journal |title=Reductions in Depression and Anxiety Among Autistic Adults Participating in an Intervention to Promote Healthy Relationships |journal=The American Journal of Occupational Therapy |date=2023 |pmc=10137597 |volume=77 |issue=2 |doi=10.5014/ajot.2023.050108 |pmid=37040101 |vauthors=Holmes LG, Goebel RJ, Hollingue C, Zhu S, Zhang H, Shan W, Wang S, Caplan R, Sanchez A, Wharmby P, Chiang M, Person M, Rothman EF}}

Other behavioral characteristics include uncommon responses to sensations (such as sights, sounds, touch, taste and smell) and difficulties keeping a consistent speech rhythm. The latter influences social skills, leading to potential difficulties in understanding for interlocutors. Autistic people show behavioral characteristics that typically influence development, language, and social competence. Their behavioral characteristics can be observed as perceptual disturbances, disturbances of development rate, relating, speech and language, and motility.{{cite book |vauthors=Hinerman PS |title=Teaching Autistic Children to Communicate |date=1983 |publisher=Aspens System Corporation |location=Rockville, Maryland |isbn=978-0-89443-884-4 |page=180}}

The second core feature of autism spectrum is a pattern of restricted and repetitive behaviors, activities, and interests. To be diagnosed with autism under the DSM-5-TR, a person must have at least two of the following behaviors:{{sfn|DSM-5-TR}}{{cite journal |vauthors=Lord C, Elsabbagh M, Baird G, Veenstra-Vanderweele J |date=August 2018 |title=Autism spectrum disorder |journal=The Lancet |volume=392 |issue=10146 |pages=508–520 |doi=10.1016/S0140-6736(18)31129-2 |pmc=7398158 |pmid=30078460 |s2cid=51922565}}

File:James arranging brads.jpg on a cork coaster]]

• Repetitive behaviors – Repetitive behaviors such as rocking, hand flapping, finger flicking, head banging, or repeating phrases or sounds.{{cite web |url=https://www.uptodate.com/contents/autism-spectrum-disorder-clinical-features |title=Autism spectrum disorder: Clinical features |vauthors=Augustyn M |website=UpToDate |access-date=22 March 2020 |archive-date=7 November 2022 |archive-url=https://web.archive.org/web/20221107065340/https://www.uptodate.com/contents/autism-spectrum-disorder-clinical-features |url-status=live}} These behaviors may occur constantly or only when the person gets stressed, anxious, or upset. These behaviors are also known as stimming.
• Resistance to change – A strict adherence to routines such as eating certain foods in a specific order or taking the same path to school every day. The person may become distressed if there is a change or disruption to their routine.
• Restricted interests – An excessive interest in a particular activity, topic, or hobby, and devoting all their attention to it. For example, young children might completely focus on things that spin and ignore everything else. Older children might try to learn everything about a single topic, such as the weather or sports, and perseverate or talk about it constantly.
• Sensory reactivity – An unusual reaction to certain sensory inputs, such as negative reaction to specific sounds or textures, fascination with lights or movements, or apparent indifference to pain or heat.{{sfn|DSM-5-TR|loc="Hyper- or hyporeactivity to sensory input or unusual interest in sensory aspects of the environment (e.g., apparent indifference to pain/temperature, adverse response to specific sounds or textures, excessive smelling or touching of objects, visual fascination with lights or movement)"}}

Autistic people can display many forms of repetitive or restricted behavior, which the Repetitive Behavior Scale-Revised (RBS-R) categorizes as follows.{{cite journal |vauthors=Lam KS, Aman MG |date=May 2007 |title=The Repetitive Behavior Scale-Revised: independent validation in individuals with autism spectrum disorders |journal=Journal of Autism and Developmental Disorders |volume=37 |issue=5 |pages=855–866 |doi=10.1007/s10803-006-0213-z |pmid=17048092 |s2cid=41034513}}

• Stereotyped behaviors: Repetitive movements, such as hand flapping, head rolling, or body rocking.
• Compulsive behaviors: Time-consuming behaviors intended to reduce anxiety, that a person feels compelled to perform repeatedly or according to rigid rules, such as placing objects in a specific order, checking things, or handwashing.
• Sameness: Resistance to change; for example, insisting that the furniture not be moved or refusing to be interrupted.
• Ritualistic behavior: Unvarying pattern of daily activities, such as an unchanging menu or a dressing ritual. This is closely associated with sameness and an independent validation has suggested combining the two factors.
• Self-injurious behaviors: Behaviors such as eye-poking, skin-picking, hand-biting and head-banging.

Self-injurious behaviors are relatively common in autistic people, and can include head-banging, self-cutting, self-biting, and hair-pulling.{{cite journal |vauthors=Minshawi NF, Hurwitz S, Fodstad JC, Biebl S, Morriss DH, McDougle CJ |title=The association between self-injurious behaviors and autism spectrum disorders |journal=Psychology Research and Behavior Management |volume=7 |pages=125–36 |date=April 2014 |pmid=24748827 |pmc=3990505 |doi=10.2147/PRBM.S44635 |doi-access=free}} Some of these can result in serious injury or death. Autistic people are about three times as likely as their non-autistic counterparts to engage in self-injury.{{Cite journal |last1=Blanchard |first1=Ashley |last2=Chihuri |first2=Stanford |last3=DiGuiseppi |first3=Carolyn G. |last4=Li |first4=Guohua |date=2021-10-01 |title=Risk of Self-harm in Children and Adults With Autism Spectrum Disorder: A Systematic Review and Meta-analysis |journal=JAMA Network Open |volume=4 |issue=10 |pages=e2130272 |doi=10.1001/jamanetworkopen.2021.30272 |issn=2574-3805 |pmc=8527356 |pmid=34665237}}

Theories about the cause of self-injurious behavior in children with developmental delay, including autistic children, include:{{cite journal |vauthors=Oliver C, Richards C |title=Practitioner Review: Self-injurious behaviour in children with developmental delay |journal=Journal of Child Psychology and Psychiatry |volume=56 |issue=10 |pages=1042–54 |date=October 2015 |pmid=25916173 |doi=10.1111/jcpp.12425 |s2cid=206034400 |url=http://pure-oai.bham.ac.uk/ws/files/26880648/Oliver_Richards_2015_Self_injurious_behaviour_children_dev._delay_JCPP.pdf |type=Review |access-date=25 August 2020 |archive-date=12 August 2023 |archive-url=https://web.archive.org/web/20230812175509/http://pure-oai.bham.ac.uk/ws/files/26880648/Oliver_Richards_2015_Self_injurious_behaviour_children_dev._delay_JCPP.pdf |url-status=live}}

• Frequency or continuation of self-injurious behavior can be influenced by environmental factors (e.g., reward in return for halting self-injurious behavior). This theory does not apply to younger children with autism. There is some evidence that frequency of self-injurious behavior can be reduced by removing or modifying environmental factors that reinforce the behavior.{{rp|10–12|}}
• Higher rates of self-injury are noted in socially isolated autistic people. Studies have shown that socialization skills are related factors to self-injurious behavior for autistic people.{{cite journal |vauthors=Flowers J, Lantz J, Hamlin T, Simeonsson RJ |title=Associated Factors of Self-injury Among Adolescents with Autism Spectrum Disorder in a Community and Residential Treatment Setting |journal=Journal of Autism and Developmental Disorders |volume=50 |issue=8 |pages=2987–3004 |date=August 2020 |pmid=32056114 |doi=10.1007/s10803-020-04389-4 |s2cid=211111895}}
• Self-injury could be a response to modulate pain perception when chronic pain or other health problems that cause pain are present.{{rp|12-13|q=In the last decade a number of studies has emerged which indicate that pain might directly cause self-injury ... Self-injury could moderate the perception of pain caused by ongoing health problem}}
• Anomalies in basal ganglia connectivity may predispose to self-injurious behavior.{{rp|13|q=In a recent review, Muehlmann and Lewis (2012) concluded that alterations in cortical basal ganglia circuitry underlie both self-injurious and stereotypic/compulsive behaviours.}}

Risk factors for self-harm and suicidality include circumstances that could affect anyone, such as mental health problems (e.g., anxiety disorder) and social problems (e.g., unemployment and social isolation), plus factors that affect only autistic people, such as actively trying to behave like a neurotypical person, which is called masking.{{Cite journal |last1=Newell |first1=Victoria |last2=Phillips |first2=Lucy |last3=Jones |first3=Chris |last4=Townsend |first4=Ellen |last5=Richards |first5=Caroline |last6=Cassidy |first6=Sarah |date=2023-03-15 |title=A systematic review and meta-analysis of suicidality in autistic and possibly autistic people without co-occurring intellectual disability |journal=Molecular Autism |volume=14 |issue=1 |page=12 |doi=10.1186/s13229-023-00544-7 |doi-access=free |issn=2040-2392 |pmid=36922899 |pmc=10018918}} Approximately 8 in 10 autistic people have a mental health problem in their lifetime, in comparison to 1 in 4 of the general population.{{cite web |title= Depression and autism |url=https://www.autistica.org.uk/what-is-autism/depression-and-autism |website= Autistica |date=14 March 2024 |access-date=23 January 2025}}{{cite web |title=Suicide and autism |url=https://www.autistica.org.uk/what-is-autism/suicide-and-autism |website=Autistica |date= 7 March 2024 |access-date=23 January 2025 |archive-url=https://web.archive.org/web/20250308021617/https://www.autistica.org.uk/what-is-autism/suicide-and-autism |archive-date=8 March 2025}}{{cite journal |first1=Anne |last1=Lever |first2= Geurts |last2=Hilde |date=2016 |title= Psychiatric Co-occurring Symptoms and Disorders in Young, Middle-Aged, and Older Adults with Autism Spectrum Disorder |pmid=26861713 |journal=Journal of Autism and Developmental Disorders |volume=46 |issue=6 |pages=1916–1930 |doi=10.1007/s10803-016-2722-8 |pmc=4860203}} A 2019 meta-analysis found autistic people to be four times more likely to have depression than non-autistic people, with approximately 40% of autistic adults having depression.{{cite journal |first1=Chloe C |last1=Hudson |first2=Layla |last2=Hall |first3=Kate L |last3=Harkness |date=2019 |title=Prevalence of Depressive Disorders in Individuals with Autism Spectrum Disorder: a Meta-Analysis |pmid=29497980 |journal=Journal of Abnormal Child Psychology |volume=47 |issue=1 |pages=165–175 |doi=10.1007/s10802-018-0402-1}}

Rates of suicidality vary significantly depending upon what is being measured. This is partly because questionnaires developed for neurotypical subjects are not always valid for autistic people. As of 2023, the Suicidal Behaviours Questionnaire–Autism Spectrum Conditions (SBQ-ASC) is the only test validated for autistic people. According to some estimates, about a quarter of autistic youth{{Cite journal |last1=O'Halloran |first1=L. |last2=Coey |first2=P. |last3=Wilson |first3=C. |date=April 2022 |title=Suicidality in autistic youth: A systematic review and meta-analysis |journal=Clinical Psychology Review |volume=93 |page=102144 |doi=10.1016/j.cpr.2022.102144 |issn=1873-7811 |pmid=35290800|doi-access=free}} and a third of all autistic people{{Cite journal |last1=Huntjens |first1=Anne |last2=Landlust |first2=Annemiek |last3=Wissenburg |first3=Sophie |last4=van der Gaag |first4=Mark |date=March 2024 |title=The Prevalence of Suicidal Behavior in Autism Spectrum Disorder |journal=Crisis |volume=45 |issue=2 |pages=144–153 |doi=10.1027/0227-5910/a000922 |issn=2151-2396 |pmid=37668055|hdl=1871.1/2e96e0d9-7230-421a-bb77-834a9c4ae2bb |url=https://pure.rug.nl/ws/files/877687272/retrieve_1_.pdf |hdl-access=free }} have experienced suicidal ideation at some point. Rates of suicidal ideation are the same for people formally diagnosed with autism and people who have typical intelligence and are believed to have autism but have not been diagnosed. The suicide rate for verbal autistics is nine times that of the general population.{{cite news |url=https://www.theguardian.com/society/2023/jul/31/autism-could-be-seen-as-part-of-personality-for-some-diagnosed-experts-say |title=Autism could be seen as part of personality for some diagnosed, experts say |first=Amelia |last=Hill |date=31 July 2023 |newspaper=The Guardian |archive-date=1 August 2023 |archive-url=https://web.archive.org/web/20230801022836/https://www.theguardian.com/society/2023/jul/31/autism-could-be-seen-as-part-of-personality-for-some-diagnosed-experts-say |url-status=live |access-date=1 August 2023}}

Most people who attempt suicide are not autistic, but autistic people are about three times as likely as non-autistic people to make a suicide attempt.{{Cite journal |last1=Santomauro |first1=Damian F. |last2=Hedley |first2=Darren |last3=Sahin |first3=Ensu |last4=Brugha |first4=Traolach S. |last5=Naghavi |first5=Mohsen |last6=Vos |first6=Theo |last7=Whiteford |first7=Harvey A. |last8=Ferrari |first8=Alize J. |last9=Stokes |first9=Mark A. |date=November 2024 |title=The global burden of suicide mortality among people on the autism spectrum: A systematic review, meta-analysis, and extension of estimates from the Global Burden of Disease Study 2021 |journal=Psychiatry Research |volume=341 |page=116150 |pmid=39197224 |doi=10.1016/j.psychres.2024.116150 |issn=1872-7123}} Less than 10% of autistic youth have attempted suicide, but 15% to 25% of autistic adults have. The suicide attempt rates are the same among people formally diagnosed with autism and those who have typical intelligence and are believed to have autism but have not been diagnosed. The suicide risk is lower among cisgender autistic males and autistic people with intellectual disabilities. The rate of suicide results in a global excess mortality among autistic people equal to approximately 2% of all suicide deaths each year.

{{Main|Autistic burnout}}

Autistic people identify a subset of burnout that interacts uniquely with characteristics and experiences of autism. This burnout is termed autistic burnout. It is a prolonged state of exhaustion that results in reduced social and occupational skill capacity and quality of life.{{Cite journal |title=Confirming the nature of autistic burnout |first1=Samuel RC |last1=Arnold |first2=Julianne M |last2=Higgins |first3=Janelle |last3=Weise |first4=Aishani |last4=Desai |first5=Elizabeth |last5=Pellicano |first6=Julian N |last6=Trollor |date=10 October 2023 |journal=Autism |volume=27 |issue=7 |pages=1906–1918 |doi=10.1177/13623613221147410 |pmid=36637293 |url=https://discovery.ucl.ac.uk/id/eprint/10163509/}} Academic and clinical research has begun on the ways in which autistic burnout is experienced.{{Cite journal |title="Having All of Your Internal Resources Exhausted Beyond Measure and Being Left with No Clean-Up Crew": Defining Autistic Burnout |first1=Dora M. |last1=Raymaker |first2=Alan R. |last2=Teo |first3=Nicole A. |last3=Steckler |first4=Brandy |last4=Lentz |first5=Mirah |last5=Scharer |first6=Austin |last6=Delos Santos |first7=Steven K. |last7=Kapp |first8=Morrigan |last8=Hunter |first9=Andee |last9=Joyce |first10=Christina |last10=Nicolaidis |date=1 June 2020 |journal=Autism in Adulthood: Challenges and Management |volume=2 |issue=2 |pages=132–143 |doi=10.1089/aut.2019.0079 |pmid=32851204 |pmc=7313636}}

Autistic people have said that autistic burnout can occur repeatedly, have cognitive and physical effects, be misunderstood by medical professionals, and adversely affect life goals in extended cases. But autistic people have also said that autistic burnout can often be a catalyst for diagnosis or other improved self-care and well-being. In particular, autistic people have anecdotally identified patterns of factors that lead to burnout.{{cite web |url=https://www.autismparentingmagazine.com/burnout-autism-prevention-causes/ |title=Autistic Burnout: Causes and Prevention Tips |date=13 September 2022 |archive-url=https://web.archive.org/web/20250323111605/https://www.autismparentingmagazine.com/burnout-autism-prevention-causes/ |archive-date=23 March 2025}} Autistic people can also derive support from community members by sharing mitigating and coping strategies.{{Cite journal |title=What Is Autistic Burnout? A Thematic Analysis of Posts on Two Online Platforms |first1=Jane |last1=Mantzalas |first2=Amanda L. |last2=Richdale |first3=Achini |last3=Adikari |first4=Jennifer |last4=Lowe |first5=Cheryl |last5=Dissanayake |date=1 March 2022 |journal=Autism in Adulthood |volume=4 |issue=1 |pages=52–65 |doi=10.1089/aut.2021.0021 |pmid=36605565 |pmc=8992925}} This is a reason that community psychology is used to study autistic communities.{{Cite thesis |degree=PhD |last=Botha |first=M |title=Autistic community connectedness as a buffer against the effects of minority stress |publisher=University of Surrey |access-date=2024-11-27 |date=2020 |url=https://openresearch.surrey.ac.uk/esploro/outputs/doctoral/99512577202346 |archive-url=https://web.archive.org/web/20250318055113/https://openresearch.surrey.ac.uk/esploro/outputs/doctoral/99512577202346 |archive-date=18 March 2025}}

Autistic people may exhibit traits or characteristics that are not part of the formal diagnostic criteria but can nonetheless affect their personal well-being or family dynamics.{{cite journal |display-authors=6 |vauthors=Filipek PA, Accardo PJ, Baranek GT, Cook EH, Dawson G, Gordon B, Gravel JS, Johnson CP, Kallen RJ, Levy SE, Minshew NJ, Ozonoff S, Prizant BM, Rapin I, Rogers SJ, Stone WL, Teplin S, Tuchman RF, Volkmar FR |date=December 1999 |title=The screening and diagnosis of autistic spectrum disorders |journal=Journal of Autism and Developmental Disorders |volume=29 |issue=6 |pages=439–484 |doi=10.1023/A:1021943802493 |pmid=10638459 |s2cid=145113684}} This paper represents a consensus of representatives from nine professional and four parent organizations in the US.

• Some autistic people show unusual or notable abilities, ranging from splinter skills (such as the memorization of trivia) to rare talents in mathematics, music, or artistic reproduction, which in exceptional cases are considered a part of the savant syndrome.{{cite journal |vauthors=Treffert DA |date=May 2009 |title=The savant syndrome: an extraordinary condition. A synopsis: past, present, future |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |volume=364 |issue=1522 |pages=1351–1357 |doi=10.1098/rstb.2008.0326 |pmc=2677584 |pmid=19528017}}{{cite journal |vauthors=Zhang Y, Han VZ |date=April 2018 |title=[Neurobiological mechanisms of autistic savant and acquired savant] |trans-title=Neurobiological mechanisms of autistic savant and acquired savant |journal=Sheng Li Xue Bao |language=zh |volume=70 |issue=2 |pages=201–210 |pmid=29691585}}{{cite journal |vauthors=Hughes JE, Ward J, Gruffydd E, Baron-Cohen S, Smith P, Allison C, Simner J |date=October 2018 |title=Savant syndrome has a distinct psychological profile in autism |journal=Molecular Autism |volume=9 |page=53 |doi=10.1186/s13229-018-0237-1 |pmc=6186137 |pmid=30344992 |doi-access=free}} One study describes how some autistic people show superior skills in perception and attention relative to the general population.{{cite journal |vauthors=Plaisted Grant K, Davis G |date=May 2009 |title=Perception and apperception in autism: rejecting the inverse assumption |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |volume=364 |issue=1522 |pages=1393–1398 |doi=10.1098/rstb.2009.0001 |pmc=2677593 |pmid=19528022}} Sensory differences are found in over 90% of autistic people, and are considered core features by some.{{cite journal |author-link=Daniel Geschwind |vauthors=Geschwind DH |year=2009 |title=Advances in autism |journal=Annual Review of Medicine |volume=60 |pages=367–380 |doi=10.1146/annurev.med.60.053107.121225 |pmc=3645857 |pmid=19630577}}
• More generally, autistic people tend to show a "spiky skills profile", with strong abilities in some areas contrasting with much weaker abilities in others.{{cite journal |vauthors=Happé F, Frith U |date=August 1996 |title=The neuropsychology of autism |journal=Brain |publisher=Oxford University Press |volume=119 |issue=4 |pages=1377–1400 |doi=10.1093/brain/119.4.1377 |pmid=8813299 |doi-access=free}}
• Differences between the previously recognized disorders under the autism spectrum are greater for under-responsivity (for example, walking into things) than for over-responsivity (for example, distress from loud noises) or for sensation seeking (for example, rhythmic movements).{{cite journal |vauthors=Ben-Sasson A, Hen L, Fluss R, Cermak SA, Engel-Yeger B, Gal E |date=January 2009 |title=A meta-analysis of sensory modulation symptoms in individuals with autism spectrum disorders |journal=Journal of Autism and Developmental Disorders |volume=39 |issue=1 |pages=1–11 |doi=10.1007/s10803-008-0593-3 |pmid=18512135 |s2cid=5208889}} An estimated 60–80% of autistic people have motor signs that include poor muscle tone, poor motor planning, and toe walking;{{cite journal |vauthors=Gargot T, Archambault D, Chetouani M, Cohen D, Johal W, Anzalone SM |date=10 January 2022 |title=Automatic Assessment of Motor Impairments in Autism Spectrum Disorders: A Systematic Review |journal=Cognitive Computation |volume=14 |issue=2 |pages=624–659 |doi=10.1007/s12559-021-09940-8 |issn=1866-9964 |s2cid=248326222 |url=https://hal.archives-ouvertes.fr/hal-03520967/file/review_article__for_Cognitive_computations__with_proper_model_.pdf |access-date=14 July 2022 |archive-date=15 December 2022 |archive-url=https://web.archive.org/web/20221215184813/https://hal.archives-ouvertes.fr/hal-03520967/file/review_article__for_Cognitive_computations__with_proper_model_.pdf |url-status=live}} difficulties in motor coordination are pervasive across the autism spectrum.{{cite journal |vauthors=Fournier KA, Hass CJ, Naik SK, Lodha N, Cauraugh JH |date=October 2010 |title=Motor coordination in autism spectrum disorders: a synthesis and meta-analysis |journal=Journal of Autism and Developmental Disorders |volume=40 |issue=10 |pages=1227–1240 |doi=10.1007/s10803-010-0981-3 |pmid=20195737 |s2cid=3469612}}{{cite journal |last1=Wang |first1=Leah A. L. |last2=Petrulla |first2=Victoria |last3=Zampella |first3=Casey J. |last4=Waller |first4=Rebecca |last5=Schultz |first5=Robert T. |date=2022 |title=Gross motor impairment and its relation to social skills in autism spectrum disorder: A systematic review and two meta-analyses. |journal=Psychological Bulletin |language=en |volume=148 |issue=3–4 |pages=273–300 |doi=10.1037/bul0000358 |issn=1939-1455 |pmc=9894569 |pmid=35511567}}
• Pathological demand avoidance can occur. People with this set of autistic characteristics are more likely to refuse to do what is asked or expected of them, even to activities they enjoy.{{Citation needed|date=March 2025}}
• Unusual or atypical eating behavior occurs in about three-quarters of children on the autism spectrum, to the extent that it was formerly a diagnostic indicator. Selectivity is the most common characteristic, although eating rituals and food refusal also occur.{{cite journal |vauthors=Dominick KC, Davis NO, Lainhart J, Tager-Flusberg H, Folstein S |year=2007 |title=Atypical behaviors in children with autism and children with a history of language impairment |journal=Research in Developmental Disabilities |publisher=Elsevier |eissn=1873-3379 |issn=0891-4222 |volume=28 |issue=2 |pages=145–162 |doi=10.1016/j.ridd.2006.02.003 |pmid=16581226}}

{{See also|Digital media use and mental health}}

In his 2015 book NeuroTribes, Steve Silberman highlights the emergence of online communities centered around autistic people, such as Autism Network International—founded by Jim Sinclair—and Wrong Planet.{{Cite book |last1=Silberman |first1=Steve |title=NeuroTribes: the legacy of autism and the future of neurodiversity |last2=Sacks |first2=Oliver W. |date=2016 |publisher=Avery, an imprint of Penguin Random House |isbn=978-0-399-18561-8 |location=New York |pages=439–455}} Silberman writes that these digital spaces offer a "natural home" for autistic people to communicate through written language. A 2022 systematic review of 21 studies found that most studies reported moderate correlations between autism, problematic internet use, and gaming disorder.{{cite journal |last1=Murray |first1=Alayna |last2=Koronczai |first2=Beatrix |last3=Király |first3=Orsolya |last4=Griffiths |first4=Mark D. |last5=Mannion |first5=Arlene |last6=Leader |first6=Geraldine |last7=Demetrovics |first7=Zsolt |year=2021 |title=Autism, Problematic Internet Use and Gaming Disorder: A Systematic Review |journal=Review Journal of Autism and Developmental Disorders |publisher=Springer |volume=9 |pages=120–140 |doi=10.1007/s40489-021-00243-0 |hdl-access=free |hdl=10379/16762}}

{{Main|Causes of autism}}

The cause of autism is unknown.{{cite book |title=Handbook of autism and pervasive developmental disorder: assessment, diagnosis, and treatment |publisher=Springer Nature |year=2022 |isbn=978-3-030-88538-0 |editor1-last=Matson |editor1-first=Johnny L. |series=Autism and Child Psychopathology Series |location=Cham |page=18 |language=en |doi=10.1007/978-3-030-88538-0 |oclc=1341298051 |quote=To date no one genetic feature or environmental cause has proven etiological in explaining most cases autism or has been able to account for rising rates of autism. |editor2-last=Sturmey |editor2-first=Peter |s2cid=251520573}}{{cite book |last1=Sauer |first1=Ann Katrin |title=Autism spectrum disorders |last2=Stanton |first2=Janelle E. |last3=Hans |first3=Sakshi |last4=Grabrucker |first4=Andreas M. |publisher=Exon Publications |others=Andreas M. Grabrucker |year=2021 |isbn=978-0-6450017-8-5 |editor-last=Grabrucker |editor-first=Andreas M. |location=Brisbane, Australia |publication-place=Brisbane |publication-date=20 August 2021 |pages=1–16 |language=en |chapter=Autism Spectrum Disorders: Etiology and Pathology |doi=10.36255/exonpublications.autismspectrumdisorders.2021.etiology |oclc=1280592589 |pmid=34495611 |quote=The cause of ASD is unknown, but several genetic and non-genetic risk factors have been characterized that, alone or in combination, are implicated in the development of ASD. |doi-access=free}}{{cite journal |last1=Kałużna-Czaplińska |first1=Joanna |last2=Żurawicz |first2=Ewa |last3=Jóźwik-Pruska |first3=Jagoda |year=2018 |title=Focus on the Social Aspect of Autism |journal=Journal of Autism and Developmental Disorders |language=en |publisher=Springer Nature |publication-date=29 November 2017 |volume=48 |issue=5 |pages=1861–1867 |doi=10.1007/s10803-017-3407-7 |issn=1573-3432 |pmc=5889772 |pmid=29188587 |quote=Despite extensive ASD research lasting more than 60 years, its causes are still unknown.}}{{cite journal |last1=Medavarapu |first1=Srinivas |last2=Marella |first2=Lakshmi Lavanya |last3=Sangem |first3=Aneela |last4=Kairam |first4=Ram |year=2019 |title=Where is the Evidence? A Narrative Literature Review of the Treatment Modalities for Autism Spectrum Disorders |journal=Cureus |language=en |publisher=Springer Nature |publication-date=16 January 2019 |volume=11 |issue=1 |pages=e3901 |doi=10.7759/cureus.3901 |issn=2168-8184 |pmc=6424545 |pmid=30911457 |quote=It is important to realize that the etiology of autism is unknown and at present, there is no cure, although there are interventions that may be effective in alleviating some symptoms and improving skills that may help autistic persons lead more productive lives. |doi-access=free}} It was long presumed a single cause at genetic, cognitive, and neural levels underpinned the social and non-social features (the classic triad).{{cite journal |vauthors=Happé F, Ronald A |date=December 2008 |title=The 'fractionable autism triad': a review of evidence from behavioural, genetic, cognitive and neural research |journal=Neuropsychology Review |volume=18 |issue=4 |pages=287–304 |doi=10.1007/s11065-008-9076-8 |pmid=18956240 |s2cid=13928876}} Increasingly, autism is assumed to be a complex condition with distinct, often co-occurring, causes for its core aspects.{{cite journal |vauthors=Happé F, Ronald A, Plomin R |date=October 2006 |title=Time to give up on a single explanation for autism |journal=Nature Neuroscience |volume=9 |issue=10 |pages=1218–1220 |doi=10.1038/nn1770 |pmid=17001340 |doi-access=free}} It is unlikely that autism has a single cause; many factors are identified in research as potential contributors. These include genetics, prenatal and perinatal (shortly after birth) factors, neuroanatomical anomalies, and environmental factors. It is possible to identify general factors, but much more difficult to pinpoint specific ones.{{cite journal |vauthors=Tager-Flusberg H |year=2010 |title=The origins of social impairments in autism spectrum disorder: studies of infants at risk |journal=Neural Networks |volume=23 |issue=8–9 |pages=1072–6 |doi=10.1016/j.neunet.2010.07.008 |pmc=2956843 |pmid=20800990}}

Research into causes has been hampered by the inability to identify biologically meaningful subgroups within the autistic population{{cite journal |vauthors=Altevogt BM, Hanson SL, Leshner AI |date=June 2008 |title=Autism and the environment: challenges and opportunities for research |url=http://pediatrics.aappublications.org/cgi/content/full/121/6/1225 |journal=Pediatrics |volume=121 |issue=6 |pages=1225–1229 |doi=10.1542/peds.2007-3000 |pmid=18519493 |archive-url=https://web.archive.org/web/20100115140620/http://pediatrics.aappublications.org/cgi/content/full/121/6/1225 |archive-date=15 January 2010 |s2cid=24595814}} and by the traditional boundaries between the disciplines of psychiatry, psychology, neurology and pediatrics.{{cite journal |vauthors=Reiss AL |date=January 2009 |title=Childhood developmental disorders: an academic and clinical convergence point for psychiatry, neurology, psychology and pediatrics |journal=Journal of Child Psychology and Psychiatry, and Allied Disciplines |issn=0021-9630 |eissn=1469-7610 |oclc=01307942 |volume=50 |issue=1–2 |pages=87–98 |doi=10.1111/j.1469-7610.2008.02046.x |pmc=5756732 |pmid=19220592}} Newer technologies such as fMRI and diffusion tensor imaging can help identify biologically relevant phenotypes (observable traits) that can be viewed on brain scans, to help further neurogenetic studies of autism;{{cite journal |vauthors=Piggot J, Shirinyan D, Shemmassian S, Vazirian S, Alarcón M |date=November 2009 |title=Neural systems approaches to the neurogenetics of autism spectrum disorders |journal=Neuroscience |volume=164 |issue=1 |pages=247–256 |doi=10.1016/j.neuroscience.2009.05.054 |pmid=19482063 |s2cid=207246176}} one example is lower activity in the fusiform face area of the brain, which is associated with a less pronounced perception of people versus objects.{{cite journal |vauthors=Levy SE, Mandell DS, Schultz RT |date=November 2009 |title=Autism |journal=The Lancet |volume=374 |issue=9701 |pages=1627–1638 |doi=10.1016/S0140-6736(09)61376-3 |pmc=2863325 |pmid=19819542}}{{Erratum|https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(11)61666-8/fulltext|doi=10.1016/S0140-6736(11)61666-8|checked=yes}} It has been proposed to classify autism using genetics as well as behavior.{{cite journal |vauthors=Stephan DA |date=January 2008 |title=Unraveling autism |journal=American Journal of Human Genetics |volume=82 |issue=1 |pages=7–9 |doi=10.1016/j.ajhg.2007.12.003 |pmc=2253980 |pmid=18179879}}

{{Main|Syndromic autism}}

Autism can be classified into two categories: "syndromic autism" and "non-syndromic autism".

Syndromic autism refers to cases where autism is one of the characteristics associated with a broader medical condition or syndrome, representing about 25% of autism cases. The causes of syndromic autism are often known, and monogenic conditions account for approximately 5% of these cases.

Non-syndromic autism, also known as classic or idiopathic autism, represents the majority of cases, and its cause is typically polygenic and unknown.

{{Main|Heritability of autism|Epigenetics of autism}}

{{See also|Missing heritability problem}}

File:Autism susceptibility genes effect on brain structure.png |volume=9 |issue=48 |page=48 |date=2018 |pmid=30237867 |pmc=6139139 |doi=10.1186/s13229-018-0229-1 |doi-access=free}} most of which influence the brain structure in a similar way.]]

Autism has a strong genetic basis, although the genetics of autism are complex and it is unclear whether autism is explained more by rare mutations with major effects, or by rare multi-gene interactions of common genetic variants.{{cite journal |vauthors=Abrahams BS, Geschwind DH |date=May 2008 |title=Advances in autism genetics: on the threshold of a new neurobiology |journal=Nature Reviews. Genetics |volume=9 |issue=5 |pages=341–355 |doi=10.1038/nrg2346 |pmc=2756414 |pmid=18414403}}{{cite journal |vauthors=Buxbaum JD |year=2009 |title=Multiple rare variants in the etiology of autism spectrum disorders |journal=Dialogues in Clinical Neuroscience |volume=11 |issue=1 |pages=35–43 |doi=10.31887/DCNS.2009.11.1/jdbuxbaum |pmc=3181906 |pmid=19432386}} Complexity arises due to interactions among multiple genes, the environment, and epigenetic factors which do not change DNA sequencing but are heritable and influence gene expression.{{cite journal |vauthors=Rapin I, Tuchman RF |date=October 2008 |title=Autism: definition, neurobiology, screening, diagnosis |journal=Pediatric Clinics of North America |volume=55 |issue=5 |pages=1129–46, viii |doi=10.1016/j.pcl.2008.07.005 |pmid=18929056}} Many genes have been associated with autism through sequencing the genomes of autistic people and their parents.{{cite journal |display-authors=6 |vauthors=Sanders SJ, He X, Willsey AJ, Ercan-Sencicek AG, Samocha KE, Cicek AE, Murtha MT, Bal VH, Bishop SL, Dong S, Goldberg AP, Jinlu C, Keaney JF, Klei L, Mandell JD, Moreno-De-Luca D, Poultney CS, Robinson EB, Smith L, Solli-Nowlan T, Su MY, Teran NA, Walker MF, Werling DM, Beaudet AL, Cantor RM, Fombonne E, Geschwind DH, Grice DE, Lord C, Lowe JK, Mane SM, Martin DM, Morrow EM, Talkowski ME, Sutcliffe JS, Walsh CA, Yu TW, Ledbetter DH, Martin CL, Cook EH, Buxbaum JD, Daly MJ, Devlin B, Roeder K, State MW |date=September 2015 |title=Insights into Autism Spectrum Disorder Genomic Architecture and Biology from 71 Risk Loci |journal=Neuron |volume=87 |issue=6 |pages=1215–1233 |doi=10.1016/j.neuron.2015.09.016 |pmc=4624267 |pmid=26402605 |author45-link=Kathryn Roeder}} But most of the mutations that increase autism likelihood have not been identified. Typically, autism cannot be traced to a Mendelian (single-gene) mutation or to a single chromosome anomalies, and none of the genetic syndromes associated with autism have been shown to selectively cause autism. Numerous genes have been found, with only small effects attributable to any particular gene. Most loci individually explain less than 1% of cases of autism.{{cite journal |vauthors=Persico AM, Napolioni V |date=August 2013 |title=Autism genetics |journal=Behavioural Brain Research |volume=251 |pages=95–112 |doi=10.1016/j.bbr.2013.06.012 |pmid=23769996 |s2cid=15721666}} {{as of|2018}}, it appeared that between 74% and 93% of autism likelihood is heritable. After an older child is diagnosed with autism, 7% to 20% of subsequent children are likely to be as well. If parents have one autistic child, they have a 2% to 8% chance of having a second child who is autistic. If the autistic child is an identical twin, the other will be autistic 36% to 95% of the time. A fraternal twin is autistic up to 31% of the time.{{cite journal |last1=Rosenberg |first1=RE |last2=Law |first2=JK |last3=Yenokyan |first3=G |last4=McGready |first4=J |last5=Kauffman |first5=WE |last6=Law |first6=PA |date=October 2009 |title=Characteristics and concordance of autism spectrum disorders among 277 twin pairs |journal=Archives of Pediatrics & Adolescent Medicine |volume=163 |issue=10 |pages=907–914 |doi=10.1001/archpediatrics.2009.98 |pmid=19805709}} The large number of autistic people with non-autistic family members may result from spontaneous structural variation, such as deletions, duplications or inversions in genetic material during meiosis.{{cite journal |vauthors=Cook EH, Scherer SW |date=October 2008 |title=Copy-number variations associated with neuropsychiatric conditions |journal=Nature |volume=455 |issue=7215 |pages=919–923 |bibcode=2008Natur.455..919C |doi=10.1038/nature07458 |pmid=18923514 |s2cid=4377899}}{{cite journal |display-authors=6 |vauthors=Brandler WM, Antaki D, Gujral M, Noor A, Rosanio G, Chapman TR, Barrera DJ, Lin GN, Malhotra D, Watts AC, Wong LC, Estabillo JA, Gadomski TE, Hong O, Fajardo KV, Bhandari A, Owen R, Baughn M, Yuan J, Solomon T, Moyzis AG, Maile MS, Sanders SJ, Reiner GE, Vaux KK, Strom CM, Zhang K, Muotri AR, Akshoomoff N, Leal SM, Pierce K, Courchesne E, Iakoucheva LM, Corsello C, Sebat J |date=April 2016 |title=Frequency and Complexity of De Novo Structural Mutation in Autism |journal=American Journal of Human Genetics |volume=98 |issue=4 |pages=667–679 |doi=10.1016/j.ajhg.2016.02.018 |pmc=4833290 |pmid=27018473}} Hence, a substantial fraction of autism cases may be traceable to genetic causes that are highly heritable but not inherited: that is, the mutation that causes the autism is not present in the parental genome.{{cite journal |vauthors=Beaudet AL |date=May 2007 |title=Autism: highly heritable but not inherited |journal=Nature Medicine |volume=13 |issue=5 |pages=534–536 |doi=10.1038/nm0507-534 |pmid=17479094 |s2cid=11673879}}

{{as of|2018}}, understanding of genetic factors influencing the likelihood of autism had shifted from a focus on a few alleles to an understanding that genetic involvement in autism is probably diffuse, depending on a large number of variants, some of which are common and have a small effect, and some of which are rare and have a large effect. While impactful rare variants in the CHD8 gene are the most commonly noted among autistic individuals, they are present in less than 0.5% of autistic people. The gene CHD8 encodes the protein chromodomain helicase DNA binding protein 8, which is a chromatin regulator enzyme that is essential during fetal development. CHD8 is an adenosine triphosphate (ATP)–dependent enzyme.{{cite journal |vauthors=Nishiyama M, Oshikawa K, Tsukada Y, Nakagawa T, Iemura S, Natsume T, Fan Y, Kikuchi A, Skoultchi AI, Nakayama KI |display-authors=6 |title=CHD8 suppresses p53-mediated apoptosis through histone H1 recruitment during early embryogenesis |journal=Nature Cell Biology |volume=11 |issue=2 |pages=172–182 |date=February 2009 |pmid=19151705 |pmc=3132516 |doi=10.1038/ncb1831 }}{{cite journal |vauthors=Ronan JL, Wu W, Crabtree GR |title=From neural development to cognition: unexpected roles for chromatin |journal=Nature Reviews Genetics |volume=14 |issue=5 |pages=347–359 |date=May 2013 |pmid=23568486 |pmc=4010428 |doi=10.1038/nrg3413 }}{{cite journal |vauthors=Thompson BA, Tremblay V, Lin G, Bochar DA |title=CHD8 is an ATP-dependent chromatin remodeling factor that regulates beta-catenin target genes |journal=Molecular and Cellular Biology |volume=28 |issue=12 |pages=3894–3904 |date=June 2008 |pmid=18378692 |pmc=2423111 |doi=10.1128/mcb.00322-08 }} The protein contains an Snf2 helicase domain that is responsible for the hydrolysis of ATP to adenosine diphosphate (ADP). CHD8 encodes a DNA helicase that functions as a repressor of transcription, remodeling chromatin structure by altering the position of nucleosomes. CHD8 negatively regulates Wnt signaling. Wnt signaling is important in the vertebrate early development and morphogenesis. It is believed that CHD8 also recruits the linker histone H1 and causes the repression of β-catenin and p53 target genes. The importance of CHD8 can be observed in studies where CHD8-knockout mice died after 5.5 embryonic days because of widespread p53-induced apoptosis. Some studies have determined the role of CHD8 in autism. CHD8 expression significantly increases during human mid-fetal development. The chromatin remodeling activity and its interaction with transcriptional regulators have shown to play an important role in autism aetiology. The developing mammalian brain has conserved CHD8 target regions that are associated with genes increasing the likelihood of autism.{{cite journal |vauthors=Sugathan A, Biagioli M, Golzio C, Erdin S, Blumenthal I, Manavalan P, Ragavendran A, Brand H, Lucente D, Miles J, Sheridan SD, Stortchevoi A, Kellis M, Haggarty SJ, Katsanis N, Gusella JF, Talkowski ME |display-authors=6 |title=CHD8 regulates neurodevelopmental pathways associated with autism spectrum disorder in neural progenitors |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=111 |issue=42 |pages=E4468–E4477 |date=October 2014 |pmid=25294932 |pmc=4210312 |doi=10.1073/pnas.1405266111 |doi-access=free |bibcode=2014PNAS..111E4468S}} CHD8 knockdown in human neural stem cells influences the regulation of genes associated with a higher chance of autism, many of which are direct CHD8 targets.{{cite journal |vauthors=Cotney J, Muhle RA, Sanders SJ, Liu L, Willsey AJ, Niu W, Liu W, Klei L, Lei J, Yin J, Reilly SK, Tebbenkamp AT, Bichsel C, Pletikos M, Sestan N, Roeder K, State MW, Devlin B, Noonan JP |display-authors=6 |title=The autism-associated chromatin modifier CHD8 regulates other autism risk genes during human neurodevelopment |journal=Nature Communications |volume=6 |issue=1 |page=6404 |date=March 2015 |pmid=25752243 |pmc=4355952 |doi=10.1038/ncomms7404 |bibcode=2015NatCo...6.6404C}} Recently CHD8 has been associated with the regulation of long non-coding RNAs (lncRNAs),{{cite journal |vauthors=Wilkinson B, Grepo N, Thompson BL, Kim J, Wang K, Evgrafov OV, Lu W, Knowles JA, Campbell DB |display-authors=6 |title=The autism-associated gene chromodomain helicase DNA-binding protein 8 (CHD8) regulates noncoding RNAs and autism-related genes |journal=Translational Psychiatry |volume=5 |issue=5 |pages=e568 |date=May 2015 |pmid=25989142 |pmc=4471293 |doi=10.1038/tp.2015.62 }} and the regulation of X chromosome inactivation (XCI) initiation, via regulation of Xist long non-coding RNA,{{Ambiguous|date=June 2022}} the master regulator of XCI,{{Ambiguous|date=June 2022}} though competitive binding to Xist regulatory regions.{{cite journal |vauthors=Cerase A, Young AN, Ruiz NB, Buness A, Sant GM, Arnold M, Di Giacomo M, Ascolani M, Kumar M, Hierholzer A, Trigiante G, Marzi SJ, Avner P |display-authors=6 |title=Chd8 regulates X chromosome inactivation in mouse through fine-tuning control of Xist expression |journal=Communications Biology |volume=4 |issue=1 |page=485 |date=April 2021 |pmid=33859315 |pmc=8050208 |doi=10.1038/s42003-021-01945-1 }}

Some autism spectrum conditions are associated with clearly genetic conditions, like fragile X syndrome, but only around 2% of autistic people have fragile X. Hypotheses from evolutionary psychiatry suggest that these genes persist because they are linked to human inventiveness, intelligence or systemising.{{cite journal |vauthors=Crespi BJ |title=Autism As a Disorder of High Intelligence |journal=Frontiers in Neuroscience |volume=10 |page=300 |date=30 June 2016 |pmid=27445671 |pmc=4927579 |doi=10.3389/fnins.2016.00300 |doi-access=free}}{{cite book |vauthors=Baron-Cohen S |title=The pattern seekers: how autism drives human invention |date=10 November 2020 |publisher=Basic Books |isbn=978-1-5416-4713-8|oclc=1204602315}}

Current research suggests that genes that increase the likelihood of autism are ones that control protein synthesis in neuronal cells in response to cell needs, activity and adhesion of neuronal cells, synapse formation and remodeling, and excitatory to inhibitory neurotransmitter balance. Therefore, although up to 1,000 different genes are thought to increase the likelihood of autism, all of them eventually influence neural development and connectivity between different functional areas of the brain in a similar manner that is characteristic of an autistic brain. Some of these genes are known to modulate production of the GABA neurotransmitter, the nervous system's main inhibitory neurotransmitter. These GABA-related genes are under-expressed in an autistic brain. On the other hand, genes controlling expression of glial and immune cells in the brain, e.g. astrocytes and microglia, respectively, are overexpressed, which correlates with increased number of glial and immune cells found in postmortem autistic brains. Some genes under investigation in autism pathophysiology are those that impacts the mTOR signaling pathway, which supports cell growth and survival.{{cite journal |vauthors=Chen JA, Peñagarikano O, Belgard TG, Swarup V, Geschwind DH |title=The emerging picture of autism spectrum disorder: genetics and pathology |journal=Annual Review of Pathology: Mechanisms of Disease |volume=10 |pages=111–44 |date=2015 |pmid=25621659 |doi=10.1146/annurev-pathol-012414-040405 |type=Review |doi-access=free}}

While these genetic variants are associated with a higher likelihood of being autistic, they do not individually determine whether someone will be autistic.{{cite journal |vauthors=Werling DM, Brand H, An JY, Stone MR, Zhu L, Glessner JT, Collins RL, Dong S, Layer RM, Markenscoff-Papadimitriou E, Farrell A, Schwartz GB, Wang HZ, Currall BB, Zhao X, Dea J, Duhn C, Erdman CA, Gilson MC, Yadav R, Handsaker RE, Kashin S, Klei L, Mandell JD, Nowakowski TJ, Liu Y, Pochareddy S, Smith L, Walker MF, Waterman MJ, He X, Kriegstein AR, Rubenstein JL, Sestan N, McCarroll SA, Neale BM, Coon H, Willsey AJ, Buxbaum JD, Daly MJ, State MW, Quinlan AR, Marth GT, Roeder K, Devlin B, Talkowski ME, Sanders SJ |display-authors=6 |title=An analytical framework for whole-genome sequence association studies and its implications for autism spectrum disorder |journal=Nature Genetics |volume=50 |issue=5 |pages=727–736 |date=April 2018 |pmid=29700473 |pmc=5961723 |doi=10.1038/s41588-018-0107-y}}

Autism may be under-diagnosed in women and girls due to an assumption that it is primarily a male condition,{{cite web |date=14 September 2018 |title=Thousands of autistic girls and women 'going undiagnosed' due to gender bias |url=https://www.theguardian.com/society/2018/sep/14/thousands-of-autistic-girls-and-women-going-undiagnosed-due-to-gender-bias |work=The Guardian |vauthors=Devlin H |access-date=15 May 2022 |archive-date=9 August 2020 |archive-url=https://web.archive.org/web/20200809115012/https://www.theguardian.com/society/2018/sep/14/thousands-of-autistic-girls-and-women-going-undiagnosed-due-to-gender-bias |url-status=live}} but through genetic phenomena such as imprinting and X linkage, conditions can occur more frequently and present more intensely in males, and theories have been put forward for a genetic reason why males are diagnosed more often, such as the imprinted brain hypothesis and the extreme male brain theory.{{cite journal |vauthors=Crespi B, Badcock C |date=June 2008 |title=Psychosis and autism as diametrical disorders of the social brain |journal=The Behavioral and Brain Sciences |volume=31 |issue=3 |pages=241–61; discussion 261–320 |doi=10.1017/S0140525X08004214 |pmid=18578904 |url=http://eprints.lse.ac.uk/21571/1/Psychosis%20and%20autism%20as%20diametrical%20disorders%20of%20the%20social%20brain%20%28LSERO%29.pdf |access-date=10 June 2022 |archive-date=12 April 2020 |archive-url=https://web.archive.org/web/20200412200311/http://eprints.lse.ac.uk/21571/1/Psychosis%20and%20autism%20as%20diametrical%20disorders%20of%20the%20social%20brain%20%28LSERO%29.pdf |url-status=live}}{{cite journal |vauthors=Crespi B, Stead P, Elliot M |date=January 2010 |title=Evolution in health and medicine Sackler colloquium: Comparative genomics of autism and schizophrenia |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=107 |issue=Suppl 1 |pages=1736–1741 |bibcode=2010PNAS..107.1736C |doi=10.1073/pnas.0906080106 |pmc=2868282 |pmid=19955444 |doi-access=free}}{{cite journal |vauthors=Baron-Cohen S, Knickmeyer RC, Belmonte MK |date=November 2005 |title=Sex differences in the brain: implications for explaining autism |url=http://irep.ntu.ac.uk/id/eprint/2710/1/219535_PubSub1971_Belmonte.pdf |journal=Science |volume=310 |issue=5749 |pages=819–823 |bibcode=2005Sci...310..819B |doi=10.1126/science.1115455 |pmid=16272115 |s2cid=44330420 |access-date=15 May 2022 |archive-date=19 July 2018 |archive-url=https://web.archive.org/web/20180719150047/http://irep.ntu.ac.uk/id/eprint/2710/1/219535_PubSub1971_Belmonte.pdf |url-status=live}}

{{See also|Refrigerator mother theory}}

Several prenatal and perinatal complications have been reported as possible factors increasing the likelihood of autism.{{cite web |first=Mark |last=Sircus |url=http://beta.asoundstrategy.com/sitemaster/userUploads/site502/multiple_causes_of_autism_spectrum_disorders.pdf |title=Multiple Causes of Autism Spectrum Disorders |publisher=International Medical Veritas Association}} These factors include maternal gestational diabetes, maternal and paternal age over 30,{{cite journal |last1=Sandin |first1=Sven |last2=Hultman |first2=Christina M. |last3=Kolevzon |first3=Alexander |last4=Gross |first4=Raz |last5=MacCabe |first5=James H. |last6=Reichenberg |first6=Abraham |year=2012 |title=Advancing Maternal Age Is Associated With Increasing Risk for Autism: A Review and Meta-Analysis |journal=Journal of the American Academy of Child & Adolescent Psychiatry |publisher=Elsevier |volume=51 |issue=5 |pages=477–486.e1 |doi=10.1016/j.jaac.2012.02.018 |pmid=22525954}}{{cite journal |last1=de Kluiver |first1=Hilde |last2=Buizer-Voskamp |first2=Jacobine E. |last3=Dolan |first3=Conor V. |last4=Boomsma |first4=Dorret I. |year=2017 |title=Paternal age and psychiatric disorders: A review |journal=American Journal of Medical Genetics |publisher=Wiley-Blackwell |volume=174 |issue=3 |pages=202–213 |doi=10.1002/ajmg.b.32508 |pmid=27770494 |pmc=5412832}}{{cite journal |last1=Wang |first1=Chengzhong |last2=Geng |first2=Hua |last3=Liu |first3=Weidong |last4=Zhang |first4=Guiqin |year=2017 |title=Prenatal, perinatal, and postnatal factors associated with autism: A meta-analysis |journal=Medicine |publisher=Lippincott Williams & Wilkins |volume=96 |issue=18 |pages=e6696 |doi=10.1097/MD.0000000000006696 |pmid=28471964 |pmc=5419910}} bleeding during pregnancy after the first trimester, use of certain prescription medication (e.g. valproate) or rubella infection during pregnancy,{{cite journal |vauthors=Duchan E, Patel DR |date=February 2012 |title=Epidemiology of autism spectrum disorders |journal=Pediatric Clinics of North America |volume=59 |issue=1 |pages=27–43, ix–x |doi=10.1016/j.pcl.2011.10.003 |pmid=22284791}} and meconium in the amniotic fluid. Research is not conclusive on the relation of these factors to autism, but each of them has been identified more frequently in children with autism compared to their siblings who do not have autism and other typically developing youth.{{cite journal |vauthors=Gardener H, Spiegelman D, Buka SL |title=Perinatal and neonatal risk factors for autism: a comprehensive meta-analysis |journal=Pediatrics |volume=128 |issue=2 |pages=344–55 |date=August 2011 |pmid=21746727 |pmc=3387855 |doi=10.1542/peds.2010-1036}} While it is unclear if any single factors during the prenatal phase influence the likelihood of autism,{{cite journal |vauthors=Gardener H, Spiegelman D, Buka SL |title=Prenatal risk factors for autism: comprehensive meta-analysis |journal=The British Journal of Psychiatry |volume=195 |issue=1 |pages=7–14 |date=July 2009 |pmid=19567888 |pmc=3712619 |doi=10.1192/bjp.bp.108.051672}} complications during pregnancy may be a factor.

There are also studies being done to test whether certain types of regressive autism have an autoimmune basis.{{cite journal |vauthors=Stefanatos GA |date=December 2008 |title=Regression in autistic spectrum disorders |journal=Neuropsychology Review |volume=18 |issue=4 |pages=305–319 |doi=10.1007/s11065-008-9073-y |pmid=18956241 |s2cid=34658024}}

Maternal nutrition and inflammation during preconception and pregnancy influences fetal neurodevelopment. Intrauterine growth restriction is associated with autism, in both term and preterm infants.{{cite journal |vauthors=Vohr BR, Poggi Davis E, Wanke CA, Krebs NF |date=April 2017 |title=Neurodevelopment: The Impact of Nutrition and Inflammation During Preconception and Pregnancy in Low-Resource Settings |journal=Pediatrics |type=Review |volume=139 |issue=Suppl 1 |pages=S38–S49 |doi=10.1542/peds.2016-2828F |pmid=28562247 |doi-access=free |s2cid=28637473}} Maternal inflammatory and autoimmune diseases may impact fetal tissues, potentially contributing to a genetic predisposition or influencing the development of the nervous system.{{cite journal |vauthors=Samsam M, Ahangari R, Naser SA |date=August 2014 |title=Pathophysiology of autism spectrum disorders: revisiting gastrointestinal involvement and immune imbalance |journal=World Journal of Gastroenterology |type=Review |volume=20 |issue=29 |pages=9942–9951 |doi=10.3748/wjg.v20.i29.9942 |pmc=4123375 |pmid=25110424 |doi-access=free}} Systematic reviews and meta-analyses have found that maternal prenatal infections, prenatal antibiotic exposure, and post-term pregnancies are associated with increased likelihood of autism in children.{{cite journal |last1=Jiang |first1=Hai-yin |last2=Xu |first2=Lian-lian |last3=Shao |first3=Li |last4=Xia |first4=Rong-man |last5=Yu |first5=Zheng-he |last6=Ling |first6=Zong-xin |last7=Yang|first7=Fan |last8=Deng |first8=Min |last9=Ruan |first9=Bing |year=2016 |title=Maternal infection during pregnancy and risk of autism spectrum disorders: A systematic review and meta-analysis |journal=Brain, Behavior, and Immunity |publisher=Elsevier |volume=58 |pages=165–172 |doi=10.1016/j.bbi.2016.06.005 |pmid=27287966}}{{cite journal |last1=Lee |first1=Eunmi |last2=Cho |first2=Jeonghyun |last3=Kim |first3=Ka Young |year=2019 |title=The Association between Autism Spectrum Disorder and Pre- and Postnatal Antibiotic Exposure in Childhood—A Systematic Review with Meta-Analysis |journal=International Journal of Environmental Research and Public Health |publisher=MDPI |volume=16 |issue=20 |page=4042 |doi=10.3390/ijerph16204042 |doi-access=free |pmid=31652518 |pmc=6843945}}{{cite journal |last1=Jenabi |first1=Ensiyeh |last2=Farashi |first2=Sajjad |last3=Salehi |first3=Amir Mohammad |last4=Parsapoor |first4=Hamideh |year=2023 |title=The association between post-term births and autism spectrum disorders: an updated systematic review and meta-analysis |journal=European Journal of Medical Research |publisher=BioMed Central |volume=28 |issue=1 |page=316 |doi=10.1186/s40001-023-01304-2 |doi-access=free |pmid=37660041 |pmc=10474756}}

Exposure to air pollution during child pregnancy, especially heavy metals and particulates, may increase the likelihood of autism.{{cite journal |vauthors=Lyall K, Schmidt RJ, Hertz-Picciotto I |date=April 2014 |title=Maternal lifestyle and environmental risk factors for autism spectrum disorders |journal=International Journal of Epidemiology |volume=43 |issue=2 |pages=443–464 |doi=10.1093/ije/dyt282 |pmc=3997376 |pmid=24518932 |doi-access=free}}{{cite journal |display-authors=6 |vauthors=Lam J, Sutton P, Kalkbrenner A, Windham G, Halladay A, Koustas E, Lawler C, Davidson L, Daniels N, Newschaffer C, Woodruff T |year=2016 |title=A Systematic Review and Meta-Analysis of Multiple Airborne Pollutants and Autism Spectrum Disorder |journal=PLOS ONE |volume=11 |issue=9 |pages=e0161851 |bibcode=2016PLoSO..1161851L |doi=10.1371/journal.pone.0161851 |pmc=5031428 |pmid=27653281 |doi-access=free}} Environmental factors that have been claimed without evidence to contribute to or exacerbate autism include certain foods, infectious diseases, solvents, PCBs, phthalates and phenols used in plastic products, brominated flame retardants, alcohol, smoking, illicit drugs, vaccines,{{cite journal |display-authors=6 |vauthors=Newschaffer CJ, Croen LA, Daniels J, Giarelli E, Grether JK, Levy SE, Mandell DS, Miller LA, Pinto-Martin J, Reaven J, Reynolds AM, Rice CE, Schendel D, Windham GC |year=2007 |title=The epidemiology of autism spectrum disorders |journal=Annual Review of Public Health |volume=28 |pages=235–58 |doi=10.1146/annurev.publhealth.28.021406.144007 |pmid=17367287 |doi-access=free}} and prenatal stress. Some, such as the MMR vaccine, have been completely disproven.{{cite journal |vauthors=Kinney DK, Munir KM, Crowley DJ, Miller AM |date=October 2008 |title=Prenatal stress and risk for autism |journal=Neuroscience and Biobehavioral Reviews |volume=32 |issue=8 |pages=1519–1532 |doi=10.1016/j.neubiorev.2008.06.004 |pmc=2632594 |pmid=18598714}}{{cite journal |vauthors=Hussain A, Ali S, Ahmed M, Hussain S |date=July 2018 |title=The Anti-vaccination Movement: A Regression in Modern Medicine |journal=Cureus |volume=10 |issue=7 |pages=e2919 |doi=10.7759/cureus.2919 |doi-access=free |pmc=6122668 |pmid=30186724}}{{cite journal |vauthors=Spencer JP, Trondsen Pawlowski RH, Thomas S |date=June 2017 |title=Vaccine Adverse Events: Separating Myth from Reality |journal=American Family Physician |volume=95 |issue=12 |pages=786–794 |pmid=28671426}}{{cite journal |vauthors=Di Pietrantonj C, Rivetti A, Marchione P, Debalini MG, Demicheli V |date=November 2021 |title=Vaccines for measles, mumps, rubella, and varicella in children |journal=The Cochrane Database of Systematic Reviews |volume=2021 |issue=11 |pages=CD004407 |doi=10.1002/14651858.CD004407.pub5 |pmc=8607336 |pmid=34806766}} Some evidence suggests a link between exposure to pesticides and autism.{{Cite journal |last1=Tessari |first1=Luca |last2=Angriman |first2=Marco |last3=Díaz-Román |first3=Amparo |last4=Zhang |first4=Junhua |last5=Conca |first5=Andreas |last6=Cortese |first6=Samuele |date=January 2022 |title=Association Between Exposure to Pesticides and ADHD or Autism Spectrum Disorder: A Systematic Review of the Literature |url=https://journals.sagepub.com/doi/10.1177/1087054720940402 |journal=Journal of Attention Disorders |language=en |volume=26 |issue=1 |pages=48–71 |doi=10.1177/1087054720940402 |pmid=32697136 |issn=1087-0547}}

{{Main|Vaccines and autism|MMR vaccine and autism}}

Parents may first become aware of autistic characteristics in their child around the time of a routine vaccination. This has led to unsupported and disproven theories blaming vaccine "overload", the vaccine preservative thiomersal, or the MMR vaccine for causing autism.{{cite journal |vauthors=Gerber JS, Offit PA |date=February 2009 |title=Vaccines and autism: a tale of shifting hypotheses |journal=Clinical Infectious Diseases |volume=48 |issue=4 |pages=456–461 |doi=10.1086/596476 |pmc=2908388 |pmid=19128068}} In 1998, British physician and academic Andrew Wakefield led a fraudulent, litigation-funded study that suggested that the MMR vaccine may cause autism.{{cite news |url=https://www.thetimes.co.uk/article/mmr-doctor-andrew-wakefield-fixed-data-on-autism-mgj82qsk50g |title=MMR doctor Andrew Wakefield fixed data on autism |vauthors=Deer B |date=8 February 2009 |newspaper=The Sunday Times |access-date=19 January 2019 |archive-date=20 March 2017 |archive-url=https://web.archive.org/web/20170320003216/http://www.thesundaytimes.co.uk/sto/public/news/article148992.ece |url-status=live}}{{cite news |url=https://www.theguardian.com/society/2010/feb/02/lancet-retracts-mmr-paper |title=Lancet retracts 'utterly false' MMR paper |vauthors=Boseley S |date=2 February 2010 |newspaper=The Guardian |access-date=19 January 2019 |archive-date=17 January 2021 |archive-url=https://web.archive.org/web/20210117232206/https://www.theguardian.com/society/2010/feb/02/lancet-retracts-mmr-paper |url-status=live}}{{cite book |chapter=Influenza Vaccine |chapter-url=https://nap.nationalacademies.org/read/13164/chapter/8 |title=Adverse Effects of Vaccines: Evidence and Causality |url=https://www.nap.edu/read/13164/ |doi=10.17226/13164 |pmid=24624471 |isbn=978-0-309-21435-3 |others=Committee to Review Adverse Effects of Vaccines, Board on Population Health and Public Health Practice |veditors=Stratton K, Ford A, Rusch E, Clayton EW |editor-link4=Ellen Wright Clayton |location=Washington, D.C. |publisher=Institute of Medicine/National Academies Press |date=August 2011 |access-date=19 January 2019 |archive-date=27 August 2021 |archive-url=https://web.archive.org/web/20210827234139/https://www.nap.edu/read/13164/chapter/1 |url-status=live}}{{cite journal |vauthors=Flaherty DK |title=The vaccine-autism connection: a public health crisis caused by unethical medical practices and fraudulent science |journal=The Annals of Pharmacotherapy |volume=45 |issue=10 |pages=1302–1304 |date=October 2011 |pmid=21917556 |doi=10.1345/aph.1Q318 |s2cid=39479569}}{{cite journal |vauthors=Godlee F, Smith J, Marcovitch H |date=January 2011 |title=Wakefield's article linking MMR vaccine and autism was fraudulent |journal=British Medical Journal |volume=342 |pages=c7452 |doi=10.1136/bmj.c7452 |pmid=21209060 |s2cid=43640126}} His co-authors have since recanted the claims made in the study.{{cite magazine |first=Maggie |last=McKee |date=4 March 2004 |title=Controversial MMR and autism study retracted |magazine=New Scientist |url=https://www.newscientist.com/article/dn4743-controversial-mmr-and-autism-study-retracted/ |archive-url=https://web.archive.org/web/20070813055100/http://www.newscientist.com/article.ns?id=dn4743 |archive-date=13 August 2007 |access-date=21 October 2015}}

Two versions of the vaccine causation hypothesis were that autism results from brain damage caused by either the MMR vaccine itself, or by mercury used as a vaccine preservative.{{cite journal |vauthors=Tan M, Parkin JE |title=Route of decomposition of thiomersal (thimerosal) |journal=International Journal of Pharmaceutics |volume=208 |issue=1–2 |pages=23–34 |date=November 2000 |pmid=11064208 |doi=10.1016/S0378-5173(00)00514-7}} No convincing scientific evidence supports these claims. They are biologically implausible, and further evidence continues to refute them, including the observation that the rate of autism continues to climb despite elimination of thimerosal from most routine vaccines given to children from birth to 6 years of age.{{cite web |title=Understanding Vaccines, Mercury and Thimerosal |url=https://www.fda.gov/media/83535/download |website=Food and Drug Administration |access-date=6 July 2023 |archive-date=6 May 2023 |archive-url=https://web.archive.org/web/20230506050839/https://www.fda.gov/media/83535/download |url-status=live}}{{cite journal |last=Dona |first=Asif |date=2006 |title=Immunizations and Autism: A Review of the Literature |url=https://www.cambridge.org/core/services/aop-cambridge-core/content/view/16B999364BFFD9F0DA3B09F25C1DE28C/S031716710000528Xa.pdf/immunizations-and-autism-a-review-of-the-literature.pdf |journal=Canadian Journal of Neurological Sciences |volume=33 |issue=4 |pages=341–346 |doi=10.1017/S031716710000528X |pmid=17168158 |s2cid=4670282 |access-date=6 July 2023 |archive-date=7 July 2023 |archive-url=https://web.archive.org/web/20230707171814/https://www.cambridge.org/core/services/aop-cambridge-core/content/view/16B999364BFFD9F0DA3B09F25C1DE28C/S031716710000528Xa.pdf/immunizations-and-autism-a-review-of-the-literature.pdf |url-status=live}}{{cite web |title=Thimerosal questions and answers |url=https://www.fda.gov/vaccines-blood-biologics/vaccines/thimerosal-vaccines-questions-and-answers |website=US FDA |date=18 February 2021 |access-date=6 July 2023 |archive-date=18 April 2023 |archive-url=https://web.archive.org/web/20230418195953/https://www.fda.gov/vaccines-blood-biologics/vaccines/thimerosal-vaccines-questions-and-answers |url-status=live}}{{cite journal |vauthors=Waterhouse L |title=Autism overflows: increasing prevalence and proliferating theories |journal=Neuropsychology Review |volume=18 |issue=4 |pages=273–286 |date=December 2008 |pmid=19015994 |doi=10.1007/s11065-008-9074-x |s2cid=8863638}}{{cite web |title=87% of Flu Vaccine Doses have Reduced or "no" (only trace amounts of) Thimerosal |url=https://www.cdc.gov/flu/prevent/vaxsupply.htm |website=Centers for Disease Control and Prevention |date=16 September 2022 |access-date=6 July 2023 |archive-date=7 July 2023 |archive-url=https://web.archive.org/web/20230707162416/https://www.cdc.gov/flu/prevent/vaxsupply.htm |url-status=live}}

A 2014 meta-analysis examined ten major studies on autism and vaccines involving 1.25 million children worldwide; it concluded that neither the vaccine preservative thimerosal (mercury), nor the MMR vaccine, which has never contained thimerosal,{{cite web |title=Frequently Asked Questions about Thimerosal |url=https://www.cdc.gov/vaccinesafety/concerns/thimerosal/faqs.html |access-date=21 February 2017 |publisher=Centers for Disease Control and Prevention |archive-date=7 May 2019 |archive-url=https://web.archive.org/web/20190507032946/https://www.cdc.gov/vaccinesafety/concerns/thimerosal/faqs.html |url-status=live}} lead to autism.{{cite journal |vauthors=Taylor LE, Swerdfeger AL, Eslick GD |title=Vaccines are not associated with autism: an evidence-based meta-analysis of case-control and cohort studies |journal=Vaccine |volume=32 |issue=29 |pages=3623–3629 |date=June 2014 |pmid=24814559 |doi=10.1016/j.vaccine.2014.04.085}} Despite this, misplaced parental concern has led to lower rates of childhood immunizations, outbreaks of previously controlled childhood diseases in some countries, and the preventable deaths of several children.Vaccines and autism:

• {{cite journal |vauthors=Doja A, Roberts W |date=November 2006 |title=Immunizations and autism: a review of the literature |journal=The Canadian Journal of Neurological Sciences. Le Journal Canadien des Sciences Neurologiques |volume=33 |issue=4 |pages=341–346 |doi=10.1017/s031716710000528x |pmid=17168158 |doi-access=free}}
• {{cite journal |vauthors=Gerber JS, Offit PA |date=February 2009 |title=Vaccines and autism: a tale of shifting hypotheses |journal=Clinical Infectious Diseases |volume=48 |issue=4 |pages=456–461 |doi=10.1086/596476 |pmc=2908388 |pmid=19128068}}
• {{cite journal |vauthors=Gross L |date=May 2009 |title=A broken trust: lessons from the vaccine--autism wars |journal=PLOS Biology |volume=7 |issue=5 |pages=e1000114 |doi=10.1371/journal.pbio.1000114 |pmc=2682483 |pmid=19478850 |doi-access=free}}
• {{cite journal |vauthors=Paul R |date=June 2009 |title=Parents ask: Am I risking autism if I vaccinate my children? |journal=Journal of Autism and Developmental Disorders |volume=39 |issue=6 |pages=962–963 |doi=10.1007/s10803-009-0739-y |pmid=19363650 |s2cid=34467853}}
• {{cite journal |vauthors=Poland GA, Jacobson RM |date=January 2011 |title=The age-old struggle against the antivaccinationists |journal=New England Journal of Medicine |volume=364 |issue=2 |pages=97–99 |doi=10.1056/NEJMp1010594 |pmid=21226573 |doi-access=free}}{{cite journal |vauthors=McBrien J, Murphy J, Gill D, Cronin M, O'Donovan C, Cafferkey MT |date=July 2003 |title=Measles outbreak in Dublin, 2000 |journal=The Pediatric Infectious Disease Journal |volume=22 |issue=7 |pages=580–584 |doi=10.1097/00006454-200307000-00002 |pmid=12867830}}

Several hypotheses have been presented that try to explain how and why people are autistic by integrating known causes (genetic and environmental effects) and findings (neurobiological and somatic). Some are more comprehensive, such as the Pathogenetic Triad, which proposes and operationalizes three core features (an autistic personality, cognitive compensation, neurobiological influences) that interact to cause autism, and the Intense World Theory, which explains autism through a hyper-active neurobiology that leads to an increased perception, attention, memory, and emotionality.{{cite journal |vauthors=Markram K, Markram H |date=21 December 2010 |title=The intense world theory - a unifying theory of the neurobiology of autism |journal=Frontiers in Human Neuroscience |type=Review |volume=4 |issue= |page=224 |doi=10.3389/fnhum.2010.00224 |pmc=3010743 |pmid=21191475 |quote=The proposed neuropathology is hyper-functioning of local neural microcircuits, best characterized by hyper-reactivity and hyper-plasticity. Such hyper-functional microcircuits are speculated to become autonomous and memory trapped leading to the core cognitive consequences of hyper-perception, hyper-attention, hyper-memory and hyper-emotionality. The theory is centered on the neocortex and the amygdala, but could potentially be applied to all brain regions. (...) This may lead to obsessively detailed information processing of fragments of the world and an involuntarily and systematic decoupling of the autist from what becomes a painfully intense world. |doi-access=free}} There are also simpler hypotheses that explain only individual parts of the neurobiology or phenotype of autism, such as mind-blindness (a decreased ability for theory of mind), the weak central coherence theory, or the extreme male brain and empathising–systemising theory.

{{See also|Evolutionary psychology|Pleiotropy#Autism and schizophrenia}}

Research exploring the evolutionary benefits of autism and associated genes has suggested that autistic people may have played a "unique role in technological spheres and understanding of natural systems" in the course of human development.{{cite web |vauthors=Spikins P |title=How our autistic ancestors played an important role in human evolution |url=https://theconversation.com/how-our-autistic-ancestors-played-an-important-role-in-human-evolution-73477 |website=The Conversation |language=en |date=27 March 2017 |access-date=28 June 2022 |archive-date=28 June 2022 |archive-url=https://web.archive.org/web/20220628105438/https://theconversation.com/how-our-autistic-ancestors-played-an-important-role-in-human-evolution-73477 |url-status=live}}{{cite book |vauthors=Spikins P |veditors=Fitzgerald M |title=Recent Advances in Autism Spectrum Disorders |volume=II |date=6 March 2013 |language=en |chapter=The Stone Age Origins of Autism}} It has been suggested that autism may have arisen as "a slight trade off for other traits that are seen as highly advantageous", providing "advantages in tool making and mechanical thinking", with speculation that the condition may "reveal itself to be the result of a balanced polymorphism, like sickle cell anemia, that is advantageous in a certain mixture of genes and disadvantageous in specific combinations".{{cite journal |vauthors=Lomelin DE |title=An Examination of Autism Spectrum Disorders in Relation to Human Evolution and Life History Theory |journal=Nebraska Anthropologist |date=2010 |volume=57 |url=https://digitalcommons.unl.edu/nebanthro/57/ |access-date=28 June 2022 |archive-date=9 May 2022 |archive-url=https://web.archive.org/web/20220509140740/https://digitalcommons.unl.edu/nebanthro/57/ |url-status=live}} In 2011, a paper in Evolutionary Psychology proposed that autistic traits, including increased spatial intelligence, concentration and memory, could have been naturally selected to enable self-sufficient foraging in a more (although not completely) solitary environment. This is called the "Solitary Forager Hypothesis".{{cite journal |vauthors=Reser JE |title=Conceptualizing the autism spectrum in terms of natural selection and behavioral ecology: the solitary forager hypothesis |journal=Evolutionary Psychology |volume=9 |issue=2 |pages=207–238 |date=May 2011 |pmid=22947969 |doi=10.1177/147470491100900209 |s2cid =25378900 |doi-access=free|pmc=10480880 }}{{cite news |title=Autism may have had advantages in humans' hunter-gatherer past, researcher believes |url=https://www.sciencedaily.com/releases/2011/06/110603122849.htm |website=ScienceDaily |agency=University of Southern California |language=en |date=3 June 2011 |access-date=28 June 2022 |archive-date=28 June 2022 |archive-url=https://web.archive.org/web/20220628105438/https://www.sciencedaily.com/releases/2011/06/110603122849.htm |url-status=live}}{{cite web |vauthors=Rudacille D |title=Lonely hunters |url=https://www.spectrumnews.org/opinion/lonely-hunters/ |website=Spectrum News |date=8 July 2011 |access-date=28 June 2022 |archive-date=16 August 2022 |archive-url=https://web.archive.org/web/20220816004226/https://www.spectrumnews.org/opinion/lonely-hunters/ |url-status=live}} A 2016 paper examines Asperger syndrome as "an alternative prosocial adaptive strategy" that may have developed as a result of the emergence of "collaborative morality" in the context of small-scale hunter-gathering, i.e., where "a positive social reputation for making a contribution to group wellbeing and survival" becomes more important than complex social understanding.{{cite journal |vauthors=Spikins P, Wright B, Hodgson D |title=Are there alternative adaptive strategies to human pro-sociality? The role of collaborative morality in the emergence of personality variation and autistic traits |journal=Time and Mind |date=1 October 2016 |volume=9 |issue=4 |pages=289–313 |doi=10.1080/1751696X.2016.1244949 |s2cid=151820168 |issn=1751-696X |doi-access=free}}

Some research suggests that recent human evolution may be a driving force in the rise of autism in recent human populations. Studies in evolutionary medicine indicate that as cultural evolution outpaces biological evolution, disorders linked to bodily dysfunction increase in prevalence due to lack of contact with pathogens and negative environmental conditions that once widely affected ancestral populations. Because natural selection favors reproduction over health and longevity, the lack of this impetus to adapt to certain harmful circumstances creates a tendency for genes in descendant populations to over-express themselves, which may cause a wide array of maladies, ranging from mental conditions to autoimmune diseases.{{cite news |last=Harvard University |date=11 January 2020 |title=Ongoing human evolution could explain recent rise in certain disorders |work=ScienceDaily |url=https://www.sciencedaily.com/releases/2010/01/100111102538.htm |access-date=24 May 2020 |archive-date=6 February 2017 |archive-url=https://web.archive.org/web/20170206012836/https://www.sciencedaily.com/releases/2010/01/100111102538.htm |url-status=live}} Conversely, noting the failure to find specific alleles that reliably cause autism or rare mutations that account for more than 5% of the heritable variation in autism established by twin and adoption studies, research in evolutionary psychiatry has concluded that it is unlikely that there is selection pressure for autism when considering that, like schizophrenics, autistic people and their siblings tend to have fewer offspring on average than non-autistic people, and instead that autism is probably better explained as a by-product of adaptive traits caused by antagonistic pleiotropy and by genes that are retained due to a fitness landscape with an asymmetric distribution.{{cite book|last=Nesse|first=Randolph M.|author-link=Randolph M. Nesse|year=2019|chapter=14. Minds Unbalanced on Fitness Cliffs|title=Good Reasons for Bad Feelings: Insights from the Frontier of Evolutionary Psychiatry|place=New York|publisher=Dutton|pages=245–261|isbn=978-1-101-98566-3}}{{cite book|last=Nesse|first=Randolph M.|editor-last=Buss|editor-first=David M.|editor-link=David Buss|year=2016|orig-date=2005|chapter=43. Evolutionary Psychology and Mental Health|title=The Handbook of Evolutionary Psychology, Volume 2: Integrations|place=Hoboken, NJ|publisher=Wiley|edition=2nd|pages=1018–1019|isbn=978-1-118-75580-8}}{{cite magazine|last=Nesse|first=Randolph M.|date=March 4, 2019|title=The Puzzle of the Unbalanced Mind|magazine=Psychology Today|url=https://www.psychologytoday.com/us/articles/201903/the-puzzle-the-unbalanced-mind|access-date=October 13, 2024}}

{{Main|Conditions comorbid to autism}}

File:Overlapping clinical phenotypes in genes associated with monogenic forms of autism spectrum disorder (ASD), dystonia, epilepsy and schizophrenia.svg showing overlapping clinical phenotypes in genes associated with monogenic forms of autism, dystonia, epilepsy and schizophrenia:

{{legend|#007fff|Genes associated with epilepsy}}

{{legend|#007f7f|Genes associated with schizophrenia}}

{{legend|#d4aaff|Genes associated with autism spectrum disorder}}

{{legend|#ff0000|Genes associated with dystonia}}]]

Autism is correlated or co-occurring with several personality traits and disorders. Comorbidity may increase with age and may complicate the course of youth on the autism spectrum and make intervention and therapy more difficult. Distinguishing between autism and other diagnoses can be challenging because the traits of autism often overlap with symptoms of other conditions, and the characteristics of autism make traditional diagnostic procedures difficult.{{cite book |title=International handbook of autism and pervasive developmental disorders |vauthors=Helverschou SB, Bakken TL, Martinsen H |publisher=Springer |year=2011 |isbn=978-1-4419-8064-9 |veditors=Matson JL, Sturmey P |location=New York |pages=53–74 |chapter=Psychiatric Disorders in People with Autism Spectrum Disorders: Phenomenology and Recognition |oclc=746203105}}{{cite journal |vauthors=Underwood L, McCarthy J, Tsakanikos E |date=September 2010 |title=Mental health of adults with autism spectrum disorders and intellectual disability |journal=Current Opinion in Psychiatry |volume=23 |issue=5 |pages=421–6 |doi=10.1097/YCO.0b013e32833cfc18 |pmid=20613532 |s2cid=13735841}}

File:Complete Spectrum of Physical Comorbidities with Autism Spectrum Disorder in a Nationwide Cohort (fig 1).png found increased risks for a multitude of co-occurring physical diseases, especially in infancy.]]

• The most common medical condition occurring in autistic people is seizure disorder or epilepsy, which occurs in 11–39% of autistic people.{{cite journal |vauthors=Ballaban-Gil K, Tuchman R |year=2000 |title=Epilepsy and epileptiform EEG: association with autism and language disorders |journal=Developmental Disabilities Research Reviews |volume=6 |issue=4 |pages=300–8 |doi=10.1002/1098-2779(2000)6:4<300::AID-MRDD9>3.0.CO;2-R |pmid=11107195 |doi-access=free}} The risk varies with age, cognitive level, and type of language impairment.{{cite journal |vauthors=Spence SJ, Schneider MT |date=June 2009 |title=The role of epilepsy and epileptiform EEGs in autism spectrum disorders |journal=Pediatric Research |volume=65 |issue=6 |pages=599–606 |doi=10.1203/PDR.0b013e31819e7168 |pmc=2692092 |pmid=19454962}}
• Tuberous sclerosis, an autosomal dominant genetic condition in which non-malignant tumors grow in the brain and on other vital organs, is present in 1–4% of autistic people.{{cite journal |vauthors=Wiznitzer M |date=September 2004 |title=Autism and tuberous sclerosis |journal=Journal of Child Neurology |volume=19 |issue=9 |pages=675–9 |doi=10.1177/08830738040190090701 |pmid=15563013 |s2cid=38157900}}
• Intellectual disabilities are some of the most common co-occurring conditions with autism. As diagnosis is increasingly being given to people with lower support needs, there is a tendency for the proportion with co-occurring intellectual disability to decrease over time. In a 2019 study, it was estimated that approximately 30–40% of people diagnosed with autism also have intellectual disability.{{cite journal |last1=Sala |first1=G. |last2=Hooley |first2=M. |last3=Attwood |first3=T. |date=2019 |title=Autism and Intellectual Disability: A Systematic Review of Sexuality and Relationship Education |journal=Sexuality and Disability |volume=37 |issue=3 |pages=353–382 |doi=10.1007/s11195-019-09577-4 |s2cid=255011485}} Recent research has suggested that autistic people with intellectual disability tend to have rarer, more harmful, genetic mutations than those found in people solely diagnosed with autism.{{cite journal |last1=Jensen |first1=M. |last2=Smolen |first2=C. |last3=Girirajan |first3=S. |date=2020 |title=Gene discoveries in autism are biased towards co-occuring with intellectual disability |journal=Journal of Medical Genetics |volume=57 |issue=9 |pages=647–652 |doi=10.1136/jmedgenet-2019-106476 |pmc=7483239 |pmid=32152248}} A number of genetic syndromes causing intellectual disability may also be co-occurring with autism, including fragile X, Down, Prader-Willi, Angelman, Williams syndrome,{{cite journal |vauthors=Zafeiriou DI, Ververi A, Vargiami E |date=June 2007 |title=Childhood autism and associated comorbidities |journal=Brain & Development |volume=29 |issue=5 |pages=257–272 |doi=10.1016/j.braindev.2006.09.003 |pmid=17084999 |s2cid=16386209}} branched-chain keto acid dehydrogenase kinase deficiency,{{cite web |last=Schenkman |first=Lauren |date=21 February 2023 |title=Dietary changes ease traits in rare autism-linked condition |url=https://www.spectrumnews.org/news/dietary-changes-ease-traits-in-rare-autism-linked-condition/ |access-date=23 February 2023 |website=Spectrum |language=en-US |archive-date=25 March 2023 |archive-url=https://web.archive.org/web/20230325004116/https://www.spectrumnews.org/news/dietary-changes-ease-traits-in-rare-autism-linked-condition/ |url-status=live}} and SYNGAP1-related intellectual disability.{{cite journal |display-authors=6 |vauthors=Satterstrom FK, Kosmicki JA, Wang J, Breen MS, De Rubeis S, An JY, Peng M, Collins R, Grove J, Klei L, Stevens C, Reichert J, Mulhern MS, Artomov M, Gerges S, Sheppard B, Xu X, Bhaduri A, Norman U, Brand H, Schwartz G, Nguyen R, Guerrero EE, Dias C, Betancur C, Cook EH, Gallagher L, Gill M, Sutcliffe JS, Thurm A, Zwick ME, Børglum AD, State MW, Cicek AE, Talkowski ME, Cutler DJ, Devlin B, Sanders SJ, Roeder K, Daly MJ, Buxbaum JD |date=February 2020 |title=Large-Scale Exome Sequencing Study Implicates Both Developmental and Functional Changes in the Neurobiology of Autism |journal=Cell |volume=180 |issue=3 |pages=568–584.e23 |doi=10.1016/j.cell.2019.12.036 |pmc=7250485 |pmid=31981491}}{{cite journal |vauthors=Holder Jr JL, Hamdan FF, Michaud JL |date=2019 |title=SYNGAP1-Related Intellectual Disability |url=https://www.ncbi.nlm.nih.gov/books/NBK537721/ |journal=Gene Reviews |type=Review |pmid=30789692 |access-date=25 July 2020 |archive-date=2 April 2021 |archive-url=https://web.archive.org/web/20210402192137/https://www.ncbi.nlm.nih.gov/books/NBK537721/ |url-status=live}}
• Learning disabilities are also highly co-occurring in autistic people. Approximately 25–75% of autistic people also have some degree of a learning disability.{{cite journal |vauthors=O'Brien G, Pearson J |date=June 2004 |title=Autism and learning disability |journal=Autism |volume=8 |issue=2 |pages=125–40 |doi=10.1177/1362361304042718 |pmid=15165430 |s2cid=17372893}} In particular, attention deficit disorder, which is generally more prevalent than autism (ca. 8% vs. 1%), is not directly related, though it is sometimes co-occurring with autism.{{cite journal |doi=10.1111/dmcn.15757 |title=Prevalence of attention-deficit/Hyperactivity disorder and autism in 12-year-old children: A population-based cohort |date=2024 |journal=Developmental Medicine & Child Neurology |volume=66 |issue=4 |pages=493–500 |pmid=37740541 |vauthors = Fast K, Wentz E, Roswall J, Strandberg M, Bergman S, Dahlgren J |doi-access=free}}
• Various anxiety disorders tend to co-occur with autism, with overall co-occurring rates of 7–84%.{{cite book |url=https://archive.org/details/childpsychopatho00mash_735 |title=Child Psychopathology |vauthors=Mash EJ, Barkley RA |publisher=The Guilford Press |year=2003 |isbn=978-1-57230-609-7 |location=New York |pages=[https://archive.org/details/childpsychopatho00mash_735/page/n421 409]–454 |url-access=limited}} They are common among children on the autism spectrum; there are no firm data, but studies have reported prevalences ranging from 11% to 84%. Many anxiety disorders have characteristics that are better explained by autism itself or are hard to distinguish from autism's features.{{cite journal |vauthors=White SW, Oswald D, Ollendick T, Scahill L |date=April 2009 |title=Anxiety in children and adolescents with autism spectrum disorders |journal=Clinical Psychology Review |volume=29 |issue=3 |pages=216–229 |doi=10.1016/j.cpr.2009.01.003 |pmc=2692135 |pmid=19223098}}
• Rates of co-occurring depression in autistic people range from 4–58%.{{cite journal |vauthors=Lainhart J |year=1999 |title=Psychiatric problems in individuals with autism, their parents and siblings |journal=International Review of Psychiatry |volume=11 |issue=4 |pages=278–298 |doi=10.1080/09540269974177}}
• The relationship between autism and schizophrenia remains a controversial subject under continued investigation, and recent meta-analyses have examined genetic, environmental, infectious, and immune factors that may be shared between the two conditions.{{cite journal |vauthors=Chisholm K, Lin A, Abu-Akel A, Wood SJ |date=August 2015 |title=The association between autism and schizophrenia spectrum disorders: A review of eight alternate models of co-occurrence |url=http://pure-oai.bham.ac.uk/ws/files/22611324/Chisholm_et_al_Association_between_autism_and_schizophrenia_2015_Post_Print.pdf |journal=Neuroscience and Biobehavioral Reviews |volume=55 |pages=173–83 |doi=10.1016/j.neubiorev.2015.04.012 |pmid=25956249 |s2cid=21450062 |access-date=20 August 2019 |archive-date=8 June 2020 |archive-url=https://web.archive.org/web/20200608221602/http://pure-oai.bham.ac.uk/ws/files/22611324/Chisholm_et_al_Association_between_autism_and_schizophrenia_2015_Post_Print.pdf |url-status=live}}{{cite journal |vauthors=Hamlyn J, Duhig M, McGrath J, Scott J |date=May 2013 |title=Modifiable risk factors for schizophrenia and autism—shared risk factors impacting on brain development |journal=Neurobiology of Disease |volume=53 |pages=3–9 |doi=10.1016/j.nbd.2012.10.023 |pmid=23123588 |s2cid=207067275}}{{cite journal |vauthors=Crespi BJ, Thiselton DL |date=October 2011 |title=Comparative immunogenetics of autism and schizophrenia |journal=Genes, Brain and Behavior |volume=10 |issue=7 |pages=689–701 |doi=10.1111/j.1601-183X.2011.00710.x |pmid=21649858 |s2cid=851655 |doi-access=free}} Oxidative stress, DNA alterations and DNA repair have been postulated to play a role in the aetiopathology of both autism and schizophrenia.{{cite journal |vauthors=Markkanen E, Meyer U, Dianov GL |date=June 2016 |title=DNA Damage and Repair in Schizophrenia and Autism: Implications for Cancer Comorbidity and Beyond |journal=International Journal of Molecular Sciences |volume=17 |issue=6 |page=856 |doi=10.3390/ijms17060856 |pmc=4926390 |pmid=27258260 |doi-access=free}}
• Difficulties in autism are often linked to behaviors that do not fit expectations, such as difficulties following directions, being cooperative, and doing things on other people's terms.{{cite journal |vauthors=Tsakanikos E, Costello H, Holt G, Sturmey P, Bouras N |date=July 2007 |title=Behaviour management problems as predictors of psychotropic medication and use of psychiatric services in adults with autism |url=http://cogprints.org/6268/2/JADD_2007.pdf |journal=Journal of Autism and Developmental Disorders |volume=37 |issue=6 |pages=1080–5 |doi=10.1007/s10803-006-0248-1 |pmid=17053989 |s2cid=14272598 |access-date=23 March 2012 |archive-date=19 May 2012 |archive-url=https://web.archive.org/web/20120519000144/http://cogprints.org/6268/2/JADD_2007.pdf |url-status=live}} Characteristics similar to those of ADHD can be part of an autism diagnosis.{{cite journal |vauthors=Rommelse NN, Franke B, Geurts HM, Hartman CA, Buitelaar JK |date=March 2010 |title=Shared heritability of attention-deficit/hyperactivity disorder and autism spectrum disorder |journal=European Child & Adolescent Psychiatry |volume=19 |issue=3 |pages=281–95 |doi=10.1007/s00787-010-0092-x |pmc=2839489 |pmid=20148275}}
• Sensory processing disorder can also co-occur with autism, with co-occurring rates of 42–88%.{{cite journal |vauthors=Baranek GT |date=October 2002 |title=Efficacy of sensory and motor interventions for children with autism |journal=Journal of Autism and Developmental Disorders |volume=32 |issue=5 |pages=397–422 |doi=10.1023/A:1020541906063 |pmid=12463517 |s2cid=16449130}}
• Starting in adolescence, some people with Asperger syndrome (26% in one sample){{cite journal |vauthors=Lugnegård T, Hallerbäck MU, Gillberg C |date=May 2012 |title=Personality disorders and autism spectrum disorders: what are the connections? |journal=Comprehensive Psychiatry |volume=53 |issue=4 |pages=333–40 |doi=10.1016/j.comppsych.2011.05.014 |pmid=21821235}} fall under the criteria for the similar condition schizoid personality disorder, which is characterized by a lack of interest in social relationships, a tendency towards a solitary or sheltered lifestyle, secretiveness, emotional coldness, detachment and apathy.{{cite journal |vauthors=Tantam D |date=December 1988 |title=Lifelong eccentricity and social isolation. II: Asperger's syndrome or schizoid personality disorder? |journal=The British Journal of Psychiatry |volume=153 |pages=783–91 |doi=10.1192/bjp.153.6.783 |pmid=3256377 |s2cid=39433805}}{{cite book |title=Integrated Treatment for Co-Occurring Disorders: Personality Disorders and Addiction |vauthors=Ekleberry SC |publisher=Routledge |year=2008 |isbn=978-0-7890-3693-3 |pages=31–32 |chapter=Cluster A - Schizoid Personality Disorder and Substance Use Disorders |chapter-url=https://books.google.com/books?id=O5HY1xcfjEcC&pg=PA31}} Asperger syndrome was traditionally called "schizoid disorder of childhood".
• Genetic conditions – about 10–15% of autism cases have an identifiable Mendelian (single-gene) condition, chromosome anomalies, or other genetic syndromes.{{cite journal |vauthors=Folstein SE, Rosen-Sheidley B |date=December 2001 |title=Genetics of autism: complex aetiology for a heterogeneous disorder |journal=Nature Reviews Genetics |volume=2 |issue=12 |pages=943–955 |doi=10.1038/35103559 |pmid=11733747 |s2cid=9331084}}
• Several metabolic defects, such as phenylketonuria, are associated with autistic features.{{cite journal |vauthors=Manzi B, Loizzo AL, Giana G, Curatolo P |date=March 2008 |title=Autism and metabolic diseases |journal=Journal of Child Neurology |volume=23 |issue=3 |pages=307–314 |doi=10.1177/0883073807308698 |pmid=18079313 |s2cid=30809774}}
• Gastrointestinal problems are one of the most commonly co-occurring medical conditions in autistic people.{{cite journal |vauthors=Israelyan N, Margolis KG |date=June 2018 |title=Serotonin as a link between the gut-brain-microbiome axis in autism spectrum disorders |journal=Pharmacological Research |type=Review |volume=132 |pages=1–6 |doi=10.1016/j.phrs.2018.03.020 |pmc=6368356 |pmid=29614380}} These are linked to greater social difficulties, irritability, language difficulties, mood changes, and behavior and sleep problems.{{cite journal |vauthors=Wasilewska J, Klukowski M |year=2015 |title=Gastrointestinal symptoms and autism spectrum disorder: links and risks - a possible new overlap syndrome |journal=Pediatric Health, Medicine and Therapeutics |type=Review |volume=6 |pages=153–166 |doi=10.2147/PHMT.S85717 |pmc=5683266 |pmid=29388597 |doi-access=free}}{{cite journal |vauthors=Rao M, Gershon MD |date=September 2016 |title=The bowel and beyond: the enteric nervous system in neurological disorders |journal=Nature Reviews. Gastroenterology & Hepatology |type=Review |volume=13 |issue=9 |pages=517–528 |doi=10.1038/nrgastro.2016.107 |pmc=5005185 |pmid=27435372 |quote=immune dysregulation, GI inflammation, malfunction of the ANS, genetic and metabolic activity of the microbiome, and dietary metabolites may contribute to brain dysfunction and neuroinflammation depending upon individual genetic vulnerability}} A 2015 review suggested that immune responses, gastrointestinal inflammation, autonomic nervous system differences, gut microbiome shifts, and food metabolites may be associated with neuroinflammation and differences in brain function. A 2016 review concludes that enteric nervous system anomalies might play a role in neurological conditions such as autism. Neural connections and the immune system may be pathways through which signals or conditions originating in the gut can influence the brain.
• Sleep problems affect about two-thirds of autistic people at some point in childhood. These most commonly include symptoms of insomnia, such as difficulty falling asleep, frequent nocturnal awakenings, and early morning awakenings. Sleep problems are associated with difficult behaviors and family stress, and are often a focus of clinical attention over and above the primary autism diagnosis.{{cite journal |vauthors=Richdale AL, Schreck KA |date=December 2009 |title=Sleep problems in autism spectrum disorders: prevalence, nature, & possible biopsychosocial aetiologies |journal=Sleep Medicine Reviews |volume=13 |issue=6 |pages=403–411 |doi=10.1016/j.smrv.2009.02.003 |pmid=19398354}}
• Dysautonomia is common in autism, affecting heart rate and blood pressure and causing symptoms such as brain fog, blurry vision, and bowel dysfunction.{{cite journal |vauthors=Al-Beltagi M|date=May 2021 |title=Autism medical comorbidities |journal=World Journal of Clinical Pediatrics |volume=10 |issue=3 |pages=15–28 |doi=10.5409/wjcp.v10.i3.15 |pmid=33972922 |pmc=8085719 |doi-access=free}}
• The frequency of autism is 10 times higher in mast cell activation syndrome patients than in the general population. This immunological condition causes cardiovascular, dermatological, gastrointestinal, neurological, and respiratory problems.{{cite journal |vauthors=Theoharides C, Angelidou A, Alysandratos K, Zhang B, Asadi S, Francis K, Taniato E, Kalegeromitros D |date=January 2022 |title=Mast cell activation and autism |journal=Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease |volume=1822 |issue= 1 |pages=34–41 |doi=10.1016/j.bbadis.2010.12.017 |pmid=21193035}}
• There is tentative evidence that gender dysphoria occurs more frequently in autistic people.{{cite journal |vauthors=Van Der Miesen AI, Hurley H, De Vries AL |year=2016 |title=Gender dysphoria and autism spectrum disorder: A narrative review |journal=International Review of Psychiatry |volume=28 |issue=1 |pages=70–80 |doi=10.3109/09540261.2015.1111199 |pmid=26753812 |s2cid=20918937 |doi-access=free}}{{cite journal |vauthors=Glidden D, Bouman WP, Jones BA, Arcelus J |date=January 2016 |title=Gender Dysphoria and Autism Spectrum Disorder: A Systematic Review of the Literature |url=https://figshare.com/articles/journal_contribution/9620366 |url-status=live |journal=Sexual Medicine Reviews |volume=4 |issue=1 |pages=3–14 |doi=10.1016/j.sxmr.2015.10.003 |pmid=27872002 |s2cid=3454600 |archive-url=https://web.archive.org/web/20231103124238/https://figshare.com/articles/journal_contribution/Gender_dysphoria_and_autism_spectrum_disorder_a_systematic_review_of_the_literature/9620366 |archive-date=3 November 2023 |access-date=19 June 2023}}

{{Main|Autism therapies}}

There is no cure for autism{{cite web |date=2 May 2019 |title=Fake and harmful autism 'treatments' |url=https://www.nhs.uk/conditions/autism/autism-and-everyday-life/fake-and-harmful-treatments/ |access-date=29 April 2022 |website=nhs.uk |language=en |archive-date=1 December 2022 |archive-url=https://web.archive.org/web/20221201180111/https://www.nhs.uk/conditions/autism/autism-and-everyday-life/fake-and-harmful-treatments/ |url-status=live}} and this may not be an appropriate goal,{{cite web |title=Making information and the words we use accessible |url=https://www.england.nhs.uk/learning-disabilities/about/get-involved/involving-people/making-information-and-the-words-we-use-accessible/ |access-date=29 April 2022 |website=NHS England |archive-date=16 July 2023 |archive-url=https://web.archive.org/web/20230716192201/https://www.england.nhs.uk/learning-disabilities/about/get-involved/involving-people/making-information-and-the-words-we-use-accessible/ |url-status=live}}{{cite web |title=How to talk about autism |url=https://www.autism.org.uk/what-we-do/help-and-support/how-to-talk-about-autism |access-date=29 April 2022 |website=autism.org.uk |language=en |archive-date=7 March 2022 |archive-url=https://web.archive.org/web/20220307130201/https://www.autism.org.uk/what-we-do/help-and-support/how-to-talk-about-autism |url-status=live}} although therapies that target handling difficulties or co-occurring conditions remain important.{{cite web |title=The psychiatric management of autism in adults (CR228) |url=https://www.rcpsych.ac.uk/improving-care/campaigning-for-better-mental-health-policy/college-reports/2020-college-reports/cr228 |access-date=29 April 2022 |website=Royal College of Psychiatrists (UK) |language=en |archive-date=2 June 2023 |archive-url=https://web.archive.org/web/20230602113739/https://www.rcpsych.ac.uk/improving-care/campaigning-for-better-mental-health-policy/college-reports/2020-college-reports/cr228 |url-status=live}} Those who have limited support needs are likely to have lessened autistic features over time.{{cite journal |vauthors=Woodbury-Smith MR, Volkmar FR |s2cid=12808995 |title=Asperger syndrome |journal=European Child & Adolescent Psychiatry |volume=18 |issue=1 |pages=2–11 |date=June 2008 |pmid=18563474 |doi=10.1007/s00787-008-0701-0 |url=http://www.ssoar.info/ssoar/handle/document/12424 |access-date=21 September 2018 |archive-date=31 March 2019 |archive-url=https://web.archive.org/web/20190331141120/https://www.ssoar.info/ssoar/handle/document/12424 |url-status=live}}{{cite journal |vauthors=Coplan J, Jawad AF |s2cid=8440775 |title=Modeling clinical outcome of children with autistic spectrum disorders |journal=Pediatrics |volume=116 |issue=1 |pages=117–22 |date=July 2005 |pmid=15995041 |doi=10.1542/peds.2004-1118}} Several therapies can help children with autism,{{cite web |title=10 Facts about Autism Spectrum Disorder (ASD) |url=https://www.acf.hhs.gov/ecd/10-facts-about-asd |access-date=6 November 2019 |website=Early Childhood Development |language=en |archive-date=6 November 2019 |archive-url=https://web.archive.org/web/20191106044902/https://www.acf.hhs.gov/ecd/10-facts-about-asd |url-status=live}} and no single one is best, with therapy typically tailored to the child's needs.{{cite journal |vauthors=Myers SM, Johnson CP |date=November 2007 |title=Management of children with autism spectrum disorders |journal=Pediatrics |volume=120 |issue=5 |pages=1162–1182 |doi=10.1542/peds.2007-2362 |pmid=17967921 |doi-access=free}} Studies of interventions have methodological problems that prevent definitive conclusions about efficacy,{{cite journal |display-authors=6 |vauthors=Ospina MB, Krebs Seida J, Clark B, Karkhaneh M, Hartling L, Tjosvold L, Vandermeer B, Smith V |year=2008 |title=Behavioural and developmental interventions for autism spectrum disorder: a clinical systematic review |journal=PLOS ONE |volume=3 |issue=11 |pages=e3755 |bibcode=2008PLoSO...3.3755O |doi=10.1371/journal.pone.0003755 |pmc=2582449 |pmid=19015734 |doi-access=free}} but the development of evidence-based interventions has advanced.

The main goals of therapy are to lessen associated difficulties and family distress, and to increase quality of life and functional independence. In general, higher IQs are correlated with higher responsiveness to interventions and larger intervention outcomes.{{cite journal |vauthors=Eldevik S, Hastings RP, Hughes JC, Jahr E, Eikeseth S, Cross S |title=Meta-analysis of Early Intensive Behavioral Intervention for children with autism |journal=Journal of Clinical Child and Adolescent Psychology |volume=38 |issue=3 |pages=439–450 |date=May 2009 |pmid=19437303 |doi=10.1080/15374410902851739 |publisher=Taylor & Francis |s2cid=205873629 |citeseerx=10.1.1.607.9620}} Behavioral, psychological, education, and skill-building interventions may be used to assist autistic people to learn life skills necessary for living independently,{{cite journal |vauthors=Matson JL, Dempsey T, Fodstad JC |title=The effect of Autism Spectrum Disorders on adaptive independent living skills in adults with severe intellectual disability |journal=Research in Developmental Disabilities |volume=30 |issue=6 |pages=1203–1211 |date=November 2009 |pmid=19450950 |doi=10.1016/j.ridd.2009.04.001 |publisher=Elsevier |eissn=1873-3379}} as well as other social, communication, and language skills. Therapy also aims to reduce behaviors that do not fit expectations and build upon strengths.{{cite web |title=NIMH » Autism Spectrum Disorder |url=https://www.nimh.nih.gov/health/publications/autism-spectrum-disorder/index.shtml |access-date=8 April 2021 |website=National Institute of Mental Health (US) |publisher=National Institutes of Health (US) |archive-date=23 April 2021 |archive-url=https://web.archive.org/web/20210423081752/https://www.nimh.nih.gov/health/publications/autism-spectrum-disorder/index.shtml |url-status=live}}

Intensive, sustained special education programs and behavior therapy early in life may help children acquire self-care, language, and job skills. Although evidence-based interventions for autistic children vary in their methods, many adopt a psychoeducational approach to enhancing cognitive, communication, and social skills while minimizing behaviors that do not fit expectations. While medications have not been found to reduce core features, they may be used for associated characteristics, such as irritability, inattention, or repetitive behavior patterns.{{cite journal |vauthors=Ji N, Findling RL |date=March 2015 |title=An update on pharmacotherapy for autism spectrum disorder in children and adolescents |journal=Current Opinion in Psychiatry |volume=28 |issue=2 |pages=91–101 |doi=10.1097/YCO.0000000000000132 |pmid=25602248 |s2cid=206141453}}

Intensive, sustained special education or remedial education programs and behavior therapy early in life may help children acquire self-care, social, and job skills. Available approaches include applied behavior analysis, developmental models, structured teaching, speech and language therapy, cognitive behavioral therapy,{{cite journal |vauthors=Wang X, Zhao J, Huang S, Chen S, Zhou T, Li Q, Luo X, Hao Y |display-authors=6 |title=Cognitive Behavioral Therapy for Autism Spectrum Disorders: A Systematic Review |journal=Pediatrics |volume=147 |issue=5 |date=May 2021 |pmid=33888566 |doi=10.1542/peds.2020-049880 |publisher=American Academy of Pediatrics (AAP) |s2cid=233370479 |doi-access=free}} social skills therapy, and occupational therapy. Among these approaches, interventions either target autistic features comprehensively or focus on a specific area of difficulty. Generally, when educating those with autism, specific tactics may be used to effectively relay information to these people. Using as much social interaction as possible is key in targeting the inhibition autistic people experience concerning person-to-person contact. Additionally, research has shown that employing semantic groupings, which involves assigning words to typical conceptual categories, can be beneficial in fostering learning.{{cite book |vauthors=Sigman M, Capps L |title=Children with Autism: A Developmental Perspective |location=Cambridge |publisher=Harvard University Press |date=2002 |pages=178–179 |isbn=978-0-674-05313-7}}

There has been increasing attention to the development of evidence-based interventions for autistic young children. Three theoretical frameworks outlined for early childhood intervention include applied behavior analysis (ABA), the developmental social-pragmatic model (DSP) and cognitive behavioral therapy (CBT). Although ABA therapy has a strong evidence base, particularly in regard to early intensive home-based therapy, ABA's effectiveness may be limited by diagnostic severity and IQ of the autistic person.{{cite journal |vauthors=Rogers SJ, Vismara LA |title=Evidence-based comprehensive treatments for early autism |journal=Journal of Clinical Child and Adolescent Psychology |publisher=Taylor & Francis |issn=1537-4416 |volume=37 |issue=1 |pages=8–38 |date=January 2008 |pmid=18444052 |pmc=2943764 |doi=10.1080/15374410701817808}} A 2015 review deemed two early childhood interventions "well-established": individual comprehensive ABA and focused teacher-implemented ABA combined with DSP.{{cite journal |vauthors=Smith T, Iadarola S |title=Evidence Base Update for Autism Spectrum Disorder |journal=Journal of Clinical Child and Adolescent Psychology |volume=44 |issue=6 |pages=897–922 |date=2015 |pmid=26430947 |doi=10.1080/15374416.2015.1077448 |publisher=Taylor & Francis |issn=1537-4416}}

Many people have criticized ABA, calling it unhelpful and unethical.{{Cite journal |last1=Sandoval-Norton |first1=Aileen Herlinda |last2=Shkedy |first2=Gary |last3=Shkedy |first3=Dalia |date=1 January 2019 |editor-last=Rushby |editor-first=Jacqueline Ann |title=How much compliance is too much compliance: Is long-term ABA therapy abuse? |journal=Cogent Psychology |language=en |volume=6 |issue=1 |doi=10.1080/23311908.2019.1641258 |issn=2331-1908 |doi-access=free }}{{Cite journal |last1=Shkedy |first1=Gary |last2=Shkedy |first2=Dalia |last3=Sandoval-Norton |first3=Aileen H. |date=June 2021 |title=Long-term ABA Therapy Is Abusive: A Response to Gorycki, Ruppel, and Zane |journal=Advances in Neurodevelopmental Disorders |language=en |volume=5 |issue=2 |pages=126–134 |doi=10.1007/s41252-021-00201-1 |issn=2366-7532 |doi-access=free }}{{Cite journal |last=Anderson |first=Laura K |date=April 2023 |title=Autistic experiences of applied behavior analysis |url=http://journals.sagepub.com/doi/10.1177/13623613221118216 |journal=Autism |language=en |volume=27 |issue=3 |pages=737–750 |doi=10.1177/13623613221118216 |pmid=35999706 |s2cid=251766661 |issn=1362-3613 |access-date=6 March 2024 |archive-date=9 September 2023 |archive-url=https://web.archive.org/web/20230909183256/https://journals.sagepub.com/doi/10.1177/13623613221118216 |url-status=live }} Sandoval-Norton et al. also discuss the "unintended but damaging consequences, such as prompt dependency, psychological abuse and compliance" that result in autistic people facing challenges as they transition into adulthood. Some ABA advocates have responded to such critiques that, instead of stopping ABA, there should be movement to increase protections and ethical compliance when working with autistic children.{{Cite journal |last1=Gorycki |first1=Kathryn A. |last2=Ruppel |first2=Paula R. |last3=Zane |first3=Thomas |date=31 December 2020 |editor-last=Navalta |editor-first=Carryl P. |title=Is long-term ABA therapy abusive: A response to Sandoval-Norton and Shkedy |url=https://www.tandfonline.com/doi/full/10.1080/23311908.2020.1823615 |journal=Cogent Psychology |language=en |volume=7 |issue=1 |doi=10.1080/23311908.2020.1823615 |issn=2331-1908 |access-date=6 March 2024 |archive-date=29 April 2023 |archive-url=https://web.archive.org/web/20230429165526/https://www.tandfonline.com/doi/full/10.1080/23311908.2020.1823615 |url-status=live |hdl=1808/31691 |hdl-access=free }}

Another evidence-based intervention that has demonstrated efficacy is a parent training model, which teaches parents how to implement various ABA and DSP techniques themselves. Various DSP programs have been developed to explicitly deliver intervention systems through at-home parent implementation.

In October 2015, the American Academy of Pediatrics (AAP) proposed new evidence-based recommendations for early interventions in autism for children under 3.{{cite journal |vauthors=Zwaigenbaum L, Bauman ML, Choueiri R, Kasari C, Carter A, Granpeesheh D, Mailloux Z, Smith Roley S, Wagner S, Fein D, Pierce K, Buie T, Davis PA, Newschaffer C, Robins D, Wetherby A, Stone WL, Yirmiya N, Estes A, Hansen RL, McPartland JC, Natowicz MR |display-authors=6 |title=Early Intervention for Children With Autism Spectrum Disorder Under 3 Years of Age: Recommendations for Practice and Research |journal=Pediatrics |volume=136 |issue=Supplement 1 |pages=S60-81 |date=October 2015 |pmid=26430170 |doi=10.1542/peds.2014-3667E |pmc=9923898 |doi-access=free}} These recommendations emphasize early involvement with both developmental and behavioral methods, support by and for parents and caregivers, and a focus on both the core and associated features of autism. But a Cochrane review found no evidence that early intensive behavioral intervention (EIBI) is effective in reducing behaviors that do not fit expectations associated with autism in most autistic children, though it did improve IQ and language skills. The Cochrane review acknowledged that this may be due to the low quality of studies available on EIBI and therefore providers should recommend EIBI based on their clinical judgment and the family's preferences. No adverse effects of EIBI were found.{{cite journal |vauthors=Reichow B, Hume K, Barton EE, Boyd BA |title=Early intensive behavioral intervention (EIBI) for young children with autism spectrum disorders (ASD) |journal=The Cochrane Database of Systematic Reviews |volume=5 |issue=10 |pages=CD009260 |date=May 2018 |pmid=29742275 |pmc=6494600 |doi=10.1002/14651858.CD009260.pub3}} A meta-analysis in that same database indicates that due to the heterology in autism, children progress to differing early intervention modalities based on ABA.

Autism intervention generally focuses on behavioral and educational approaches to target its two core features: social communication difficulties and restricted, repetitive behaviors. If characteristics continue after behavioral strategies have been implemented, some medications can be recommended to target specific characteristics such as restricted and repetitive behaviors (RRBs) or co-existing problems such as anxiety, depression, hyperactivity/inattention and sleep disturbance.{{cite web |url=https://www.uptodate.com/contents/autism-spectrum-disorder-in-children-and-adolescents-pharmacologic-interventions |title=Autism spectrum disorder in children and adolescents: Pharmacologic interventions |vauthors=Weissman L |date=March 2020 |access-date=17 March 2020 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920172640/https://www.uptodate.com/contents/autism-spectrum-disorder-in-children-and-adolescents-pharmacologic-interventions |url-status=live}} Melatonin, for example, can be used for sleep problems.{{cite journal |vauthors=Williams Buckley A, Hirtz D, Oskoui M, et al |title=Practice guideline: Treatment for insomnia and disrupted sleep behavior in children and adolescents with autism spectrum disorder: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology |journal=Neurology |volume=94 |issue=9 |pages=392–404 |date=March 2020 |pmid=32051244 |pmc=7238942 |doi=10.1212/WNL.0000000000009033}}

Several parent-mediated behavioral therapies target social communication difficulties in children with autism, but their efficacy in reducing RRBs is uncertain.{{cite journal |vauthors=Harrop C |title=Evidence-based, parent-mediated interventions for young children with autism spectrum disorder: The case of restricted and repetitive behaviors |language=en-US |journal=Autism |volume=19 |issue=6 |pages=662–72 |date=August 2015 |pmid=25186943 |doi=10.1177/1362361314545685 |s2cid=32326472}}

File:Opening a window to the autistic brain.jpg |volume=2 |issue=8 |pages=E267 |doi=10.1371/journal.pbio.0020267 |pmc=509312 |pmid=15314667 |doi-access=free}}]]

Educational interventions often used include applied behavior analysis (ABA), developmental models, structured teaching, speech and language therapy and social skills therapy. Among these approaches, interventions either target autistic features comprehensively or focus on a specific area of difficulty.

The quality of research for early intensive behavioral intervention (EIBI)—a procedure incorporating over 30 hours per week of the structured type of ABA that is carried out with very young children—is low; more vigorous research designs with larger sample sizes are needed. Two theoretical frameworks outlined for early childhood intervention include structured and naturalistic ABA interventions, and developmental social pragmatic models (DSP). One interventional strategy utilizes a parent training model, which teaches parents how to implement various ABA and DSP techniques, allowing for parents to disseminate interventions themselves. Various DSP programs have been developed to explicitly deliver intervention systems through at-home parent implementation. Despite the recent development of parent training models, these interventions have demonstrated effectiveness in numerous studies. Early, intensive ABA therapy has demonstrated effectiveness in enhancing communication and adaptive functioning in preschool children;{{cite journal |last=Virués-Ortega |first=Javier |date=1 June 2010 |title=Applied behavior analytic intervention for autism in early childhood: Meta-analysis, meta-regression and dose–response meta-analysis of multiple outcomes |url=https://www.sciencedirect.com/science/article/pii/S0272735810000218 |journal=Clinical Psychology Review |language=en |volume=30 |issue=4 |pages=387–399 |doi=10.1016/j.cpr.2010.01.008 |pmid=20223569 |issn=0272-7358 |access-date=17 June 2023 |archive-date=3 November 2023 |archive-url=https://web.archive.org/web/20231103124300/https://www.sciencedirect.com/science/article/abs/pii/S0272735810000218 |url-status=live}} it is also well-established for improving the intellectual performance of that age group.

In 2018, a Cochrane meta-analysis database concluded that some recent research is beginning to suggest that because of the heterology of autism, there are two different ABA teaching approaches to acquiring spoken language: children with higher receptive language skills respond to 2.5 to 20 hours per week of the naturalistic approach, whereas children with lower receptive language skills require 25 hours per week of discrete trial training—the structured and intensive form of ABA.{{cite journal |vauthors=Brignell A, Chenausky KV, Song H, Zhu J, Suo C, Morgan AT |title=Communication interventions for autism spectrum disorder in minimally verbal children |doi-access=free |journal=The Cochrane Database of Systematic Reviews |volume=2018 |issue=11 |pages=CD012324 |date=November 2018 |pmid=30395694 |pmc=6516977 |doi=10.1002/14651858.CD012324.pub2}} A 2023 multi-site randomized control trial study of 164 participants showed similar findings.{{cite journal |last1=Kasari |first1=Connie |last2=Shire |first2=Stephanie |last3=Shih |first3=Wendy |last4=Landa |first4=Rebecca |last5=Levato |first5=Lynne |last6=Smith |first6=Tristram |title=Spoken language outcomes in limited language preschoolers with autism and global developmental delay: RCT of early intervention approaches |journal=Autism Research |date=June 2023 |volume=16 |issue=6 |pages=1236–1246 |doi=10.1002/aur.2932 |pmc=10460274 |pmid=37070270 |doi-access=free}}

Similarly, a teacher-implemented intervention that utilizes a more naturalistic form of ABA combined with a developmental social pragmatic approach has been found to be beneficial for social-communication skills in young children, although there is less evidence for its reduction of global autistic characteristics. Neuropsychological reports are often poorly communicated to educators, resulting in a gap between what a report recommends and what education is provided.{{cite journal |vauthors=Kanne SM, Randolph JK, Farmer JE |date=December 2008 |title=Diagnostic and assessment findings: a bridge to academic planning for children with autism spectrum disorders |journal=Neuropsychology Review |volume=18 |issue=4 |pages=367–384 |doi=10.1007/s11065-008-9072-z |pmid=18855144 |s2cid=21108225}} The appropriateness of including autistic children with varying levels of support needs in the general education population is a subject of current debate among educators and researchers.{{cite journal |vauthors=Simpson RL, de Boer-Ott SR, Smith-Myles B |year=2003 |title=Inclusion of Learners with Autism Spectrum Disorders in General Education Settings |url=https://www.researchgate.net/publication/232218452_Inclusion_of_Learners_with_Autism_Spectrum_Disorders_in_General_Education_Settings |journal=Topics in Language Disorders |volume=23 |issue=2 |pages=116–133 |doi=10.1097/00011363-200304000-00005 |s2cid=143733343 |archive-url=https://web.archive.org/web/20110714215923/http://www.nursingcenter.com/pdf.asp?AID=520301 |archive-date=14 July 2011}}

Medications may be used to target autistic features that interfere with integrating a child into home or school when behavioral intervention fails.{{cite journal |vauthors=Sanchack KE, Thomas CA |date=December 2016 |title=Autism Spectrum Disorder: Primary Care Principles |journal=American Family Physician |volume=94 |issue=12 |pages=972–979 |pmid=28075089}} They may also be used for associated health problems, such as ADHD, anxiety, or if the person is hurting themself or aggressive with others,{{cite journal |last1=Iffland |first1=Michelle |last2=Livingstone |first2=Nuala |last3=Jorgensen |first3=Mikaela |last4=Hazell |first4=Philip |last5=Gillies |first5=Donna |date=9 October 2023 |editor-last=Cochrane Developmental, Psychosocial and Learning Problems Group |title=Pharmacological intervention for irritability, aggression, and self-injury in autism spectrum disorder (ASD) |journal=The Cochrane Database of Systematic Reviews |language=en |volume=2023 |issue=10 |pages=CD011769 |doi=10.1002/14651858.CD011769.pub2 |pmc=10561353 |pmid=37811711}} but their routine prescription for autism's core features is not recommended.{{cite journal |vauthors=Siafis S, Çıray O, Wu H, Schneider-Thoma J, Bighelli I, Krause M, Rodolico A, Ceraso A, Deste G, Huhn M, Fraguas D, San José Cáceres A, Mavridis D, Charman T, Murphy DG, Parellada M, Arango C, Leucht S |date=2022 |title=Pharmacological and dietary-supplement treatments for autism spectrum disorder: a systematic review and network meta-analysis |journal=Molecular Autism |volume=13 |issue=1 |page=10 |doi=10.1186/s13229-022-00488-4 |pmid=35246237|pmc=8896153 |doi-access=free}} More than half of US children diagnosed with autism are prescribed psychoactive drugs or anticonvulsants, with the most common drug classes being antidepressants, stimulants, and antipsychotics.{{cite journal |vauthors=Oswald DP, Sonenklar NA |date=June 2007 |title=Medication use among children with autism spectrum disorders |journal=Journal of Child and Adolescent Psychopharmacology |volume=17 |issue=3 |pages=348–355 |doi=10.1089/cap.2006.17303 |pmid=17630868}}{{cite journal |vauthors=Doyle CA, McDougle CJ |date=September 2012 |title=Pharmacologic treatments for the behavioral symptoms associated with autism spectrum disorders across the lifespan |journal=Dialogues in Clinical Neuroscience |volume=14 |issue=3 |pages=263–279 |doi=10.31887/DCNS.2012.14.3/cdoyle |pmc=3513681 |pmid=23226952}} The atypical antipsychotic drugs risperidone and aripiprazole are FDA-approved for reducing associated aggressive and self-injurious behaviors.{{cite journal |vauthors=Leskovec TJ, Rowles BM, Findling RL |year=2008 |title=Pharmacological treatment options for autism spectrum disorders in children and adolescents |journal=Harvard Review of Psychiatry |volume=16 |issue=2 |pages=97–112 |doi=10.1080/10673220802075852 |pmid=18415882 |s2cid=26112061}} But their side effects must be weighed against their potential benefits, and autistic people may respond atypically. Side effects may include weight gain, tiredness, drooling, and paradoxical aggression. Some emerging data show that aripiprazole and risperidone may reduce restricted and repetitive behaviors (i.e., stimming; e.g., flapping, twisting, complex whole-body movements), but due to the small sample size and different focus of these studies and the concerns about their side effects, antipsychotics are not recommended as primary ways to target RRBs.{{cite journal |vauthors=Ameis SH, Kassee C, Corbett-Dick P, Cole L, Dadhwal S, Lai MC, Veenstra-VanderWeele J, Correll CU |display-authors=6 |title=Systematic review and guide to management of core and psychiatric symptoms in youth with autism |journal=Acta Psychiatrica Scandinavica |volume=138 |issue=5 |pages=379–400 |date=November 2018 |pmid=29904907 |doi=10.1111/acps.12918 |s2cid=49209337}} SSRI antidepressants, such as fluoxetine and fluvoxamine, have been shown to be effective in reducing repetitive and ritualistic behaviors, while the stimulant medication methylphenidate can reduce co-occurring inattentiveness or hyperactivity in some children with these characteristics. There is scant reliable research about the effectiveness or safety of pharmacological approaches for autistic adolescents and adults.{{cite journal |last1=Broadstock |first1=Marita |last2=Doughty |first2=Carolyn |last3=Eggleston |first3=Matt |year=2007 |title=Systematic review of the effectiveness of pharmacological treatments for adolescents and adults with autism spectrum disorder |journal=Autism |volume=11 |issue=4 |pages=335–348 |doi=10.1177/1362361307078132 |issn=1362-3613 |pmid=17656398 |s2cid=42629626}} No known medication is approved for reducing autism's core features of social and communication difficulties, although animal models indicate that postnatal administration of MDMA may be effective.{{Cite journal |last1=Chaliha |first1=Devahuti |last2=Mamo |first2=John C. |last3=Albrecht |first3=Matthew |last4=Lam |first4=Virginie |last5=Takechi |first5=Ryu |last6=Vaccarezza |first6=Mauro |date=2021-06-23 |title=A Systematic Review of the MDMA Model to Address Social Impairment in Autism |journal=Current Neuropharmacology |volume=19 |issue=7 |pages=1101–1154 |doi=10.2174/1570159X19666210101130258 |issn=1570-159X |pmc=8686313 |pmid=33388021}} MDMA has also been investigated alongside psychotherapy to treat co-occurring social anxiety in autistic adults.{{Cite journal |last1=Danforth |first1=Alicia L. |last2=Struble |first2=Christopher M. |last3=Yazar-Klosinski |first3=Berra |last4=Grob |first4=Charles S. |date=2016-01-04 |title=MDMA-assisted therapy: A new treatment model for social anxiety in autistic adults |journal=Progress in Neuro-Psychopharmacology and Biological Psychiatry |volume=64 |pages=237–249 |doi=10.1016/j.pnpbp.2015.03.011 |pmid=25818246 |issn=0278-5846 |doi-access=free}}

A multitude of alternative therapies have been researched and implemented, and many have resulted in harm to autistic people. A 2020 systematic review on adults with autism provided evidence that mindfulness-based interventions may decrease stress, anxiety, ruminating thoughts, anger, and aggression and improve mental health.{{cite journal |display-authors=6 |vauthors=Benevides TW, Shore SM, Andresen ML, Caplan R, Cook B, Gassner DL, Erves JM, Hazlewood TM, King MC, Morgan L, Murphy LE, Purkis Y, Rankowski B, Rutledge SM, Welch SP, Wittig K |date=August 2020 |title=Interventions to address health outcomes among autistic adults: A systematic review |journal=Autism |volume=24 |issue=6 |pages=1345–1359 |doi=10.1177/1362361320913664 |pmc=7787674 |pmid=32390461 |doi-access=free}}

Although popularly used as an alternative treatment for autistic people, {{as of|2018|lc=y}} there is no good evidence to recommend a gluten- and casein-free diet as a standard intervention.{{cite journal |vauthors=Gogou M, Kolios G |date=June 2018 |title=Are therapeutic diets an emerging additional choice in autism spectrum disorder management? |journal=World Journal of Pediatrics |type=Review |volume=14 |issue=3 |pages=215–223 |doi=10.1007/s12519-018-0164-4 |pmid=29846886 |quote=Current literature knowledge provides evidence that ketogenic and casein/gluten-free diet may have their own place in our reserve for the therapeutic management of specific subsets of children with autism. ... More clinical studies about the effect of gluten/caseinfree diet in these patients are available. However, available data arise from studies with small sample size and are still controversial. In general, despite encouraging data, no definite proof still exists. Under this view, the use of therapeutic diets in children with autism should be restricted to specific subgroups, such as children with autism and epilepsy or specific inborn errors of metabolism (ketogenic diet), children with known food intolerance/allergy or even children with food intolerance markers (gluten- and casein-free diet). Their implementation should always be guided by health care practitioners. |s2cid=44155118}}{{cite journal |vauthors=Marí-Bauset S, Zazpe I, Mari-Sanchis A, Llopis-González A, Morales-Suárez-Varela M |date=December 2014 |title=Evidence of the gluten-free and casein-free diet in autism spectrum disorders: a systematic review |journal=Journal of Child Neurology |volume=29 |issue=12 |pages=1718–1727 |doi=10.1177/0883073814531330 |pmid=24789114 |hdl-access=free |s2cid=19874518 |hdl=10171/37087}}{{cite journal |vauthors=Millward C, Ferriter M, Calver S, Connell-Jones G |date=April 2008 |title=Gluten- and casein-free diets for autistic spectrum disorder |journal=The Cochrane Database of Systematic Reviews |issue=2 |pages=CD003498 |doi=10.1002/14651858.CD003498.pub3 |pmc=4164915 |pmid=18425890 |quote=Knivsberg 2002 "monitoring of the compliance with diet was not carried out" ... "several reports of children 'sneaking food' from siblings or classmates" |veditors=Ferriter M}} A 2018 review concluded that it may be a therapeutic option for specific groups of children with autism, such as those with known food intolerances or allergies, or with food intolerance markers. The authors analyzed the prospective trials conducted to date that studied the efficacy of the gluten- and casein-free diet in children on the autism spectrum (4 in total). All of them compared gluten- and casein-free diet versus normal diet with a control group (2 double-blind randomized controlled trials, 1 double-blind crossover trial, 1 single-blind trial). In two of the studies, whose duration was 12 and 24 months, a significant reduction in autistic characteristics (efficacy rate 50%) was identified. In the other two studies, whose duration was 3 months, no significant effect was observed. The authors concluded that a longer duration of the diet may be necessary to achieve the reduction of the autistic features. Other problems documented in the trials carried out include transgressions of the diet, small sample size, the heterogeneity of the participants and the possibility of a placebo effect.{{cite journal |display-authors=6 |vauthors=Hyman SL, Stewart PA, Foley J, Cain U, Peck R, Morris DD, Wang H, Smith T |date=January 2016 |title=The Gluten-Free/Casein-Free Diet: A Double-Blind Challenge Trial in Children with Autism |journal=Journal of Autism and Developmental Disorders |volume=46 |issue=1 |pages=205–220 |doi=10.1007/s10803-015-2564-9 |pmid=26343026 |quote=20 natural challenges when parents reported that children by mistake consumed foods containing gluten or casein. |s2cid=12884691}}{{cite journal |vauthors=Siafis S, Çıray O, Schneider-Thoma J, Bighelli I, Krause M, Rodolico A, Ceraso A, Deste G, Huhn M, Fraguas D, Mavridis D, Charman T, Murphy DG, Parellada M, Arango C, Leucht S |date=2020 |title=Placebo response in pharmacological and dietary supplement trials of autism spectrum disorder (ASD): systematic review and meta-regression analysis |journal=Molecular Autism |volume=11 |issue=1 |page=66 |doi=10.1186/s13229-020-00372-z |pmid=32847616 |pmc=7448339 |doi-access=free}} In the subset of people who have gluten sensitivity there is limited evidence that suggests that a gluten-free diet may reduce some autistic behaviors.{{cite journal |vauthors=Buie T |date=May 2013 |title=The relationship of autism and gluten |journal=Clinical Therapeutics |type=Review |volume=35 |issue=5 |pages=578–583 |doi=10.1016/j.clinthera.2013.04.011 |pmid=23688532 |quote=At this time, the studies attempting to treat symptoms of autism with diet have not been sufficient to support the general institution of a gluten-free or other diet for all children with autism. There may be a subgroup of patients who might benefit from a gluten-free diet, but the symptom or testing profile of these candidates remains unclear. |doi-access=free}}{{cite journal |vauthors=Volta U, Caio G, De Giorgio R, Henriksen C, Skodje G, Lundin KE |date=June 2015 |title=Non-celiac gluten sensitivity: a work-in-progress entity in the spectrum of wheat-related disorders |journal=Best Practice & Research. Clinical Gastroenterology |volume=29 |issue=3 |pages=477–491 |doi=10.1016/j.bpg.2015.04.006 |pmid=26060112 |quote=autism spectrum disorders (ASD) have been hypothesized to be associated with NCGS [47,48]. Notably, a gluten- and casein-free diet might have a positive effect in improving hyperactivity and mental confusion in some patients with ASD. This very exciting association between NCGS and ASD deserves further study before conclusions can be firmly drawn}}{{cite journal |vauthors=San Mauro Martín I, Garicano Vilar E, Collado Yurrutia L, Ciudad Cabañas MJ |date=December 2014 |title=[Is gluten the great etiopathogenic agent of disease in the XXI century?] |trans-title=Is gluten the great etiopathogenic agent of disease in the XXI century? |journal=Nutricion Hospitalaria |language=es |volume=30 |issue=6 |pages=1203–1210 |doi=10.3305/nh.2014.30.6.7866 |pmid=25433099}}

The preference that autistic children have for unconventional foods can lead to reduction in bone cortical thickness with this risk being greater in those on casein-free diets, as a consequence of the low intake of calcium and vitamin D; however, suboptimal bone development in autism has also been associated with lack of exercise and gastrointestinal disorders.{{cite journal |vauthors=Tye C, Runicles AK, Whitehouse AJ, Alvares GA |year=2019 |title=Characterizing the Interplay Between Autism Spectrum Disorder and Comorbid Medical Conditions: An Integrative Review |journal=Frontiers in Psychiatry |type=Review |volume=9 |page=751 |doi=10.3389/fpsyt.2018.00751 |pmc=6354568 |pmid=30733689 |doi-access=free}} In 2005, botched chelation therapy killed a five-year-old child with autism.{{cite journal |vauthors=Levy SE, Hyman SL |date=October 2008 |title=Complementary and alternative medicine treatments for children with autism spectrum disorders |journal=Child and Adolescent Psychiatric Clinics of North America |type=Review |volume=17 |issue=4 |pages=803–20, ix |doi=10.1016/j.chc.2008.06.004 |pmc=2597185 |pmid=18775371}}{{cite journal |vauthors=Brown MJ, Willis T, Omalu B, Leiker R |date=August 2006 |title=Deaths resulting from hypocalcemia after administration of edetate disodium: 2003-2005 |url=http://pediatrics.aappublications.org/cgi/content/full/118/2/e534 |journal=Pediatrics |volume=118 |issue=2 |pages=e534–e536 |doi=10.1542/peds.2006-0858 |pmid=16882789 |archive-url=https://web.archive.org/web/20090727080307/http://pediatrics.aappublications.org/cgi/content/full/118/2/e534 |archive-date=27 July 2009 |s2cid=28656831}} Chelation is not recommended for autistic people since the associated risks outweigh any potential benefits.{{cite journal |vauthors=James S, Stevenson SW, Silove N, Williams K |date=May 2015 |title=Chelation for autism spectrum disorder (ASD) |journal=The Cochrane Database of Systematic Reviews |type=Review |issue=5 |pages=CD010766 |doi=10.1002/14651858.CD010766 |pmid=26106752 |veditors=James S |doi-access=free}} Another alternative medicine practice with no evidence is CEASE therapy, a pseudoscientific mixture of homeopathy, supplements, and "vaccine detoxing".{{cite web |vauthors=Loftus Y |date=24 November 2021 |title=CEASE Therapy for Autism: the Controversy of a "Cure" |url=https://www.autismparentingmagazine.com/cease-therapy-controversy-cure/ |url-status=live |archive-url=https://web.archive.org/web/20220922123637/https://www.autismparentingmagazine.com/cease-therapy-controversy-cure/ |archive-date=22 September 2022 |access-date=22 September 2022 |website=Autism Parenting Magazine}}

Results of a systematic review on interventions to address health outcomes among autistic adults found emerging evidence to support mindfulness-based interventions for improving mental health. This includes decreasing stress, anxiety, ruminating thoughts, anger, and aggression. An updated Cochrane review (2022) found evidence that music therapy likely supports the development of skills in social interaction, verbal communication, and nonverbal communication.{{cite journal |vauthors=Geretsegger M, Fusar-Poli L, Elefant C, Mössler KA, Vitale G, Gold C |title=Music therapy for autistic people |journal=The Cochrane Database of Systematic Reviews |volume=2022 |issue=5 |pages=CD004381 |date=May 2022 |pmid=35532041 |pmc=9082683 |doi=10.1002/14651858.CD004381.pub4}} There has been early research on hyperbaric oxygen therapy in children with autism.{{cite report |url=https://www.ncbi.nlm.nih.gov/books/NBK56343/ |title=Therapies for Children With Autism Spectrum Disorders |date=April 2011 |publisher=Agency for Healthcare Research and Quality (US) |page=8 |pmid=21834171 |quote=Hyperbaric therapy, in which oxygen is administered in special chambers that maintain a higher air pressure, has shown possible effects in other chronic neurologic conditions and has also undergone preliminary exploration in ASDs. |type=Report No. 11-EHC029-EF |vauthors=Warren Z, Veenstra-VanderWeele J, Stone W, etal |access-date=15 May 2022 |archive-date=8 June 2023 |archive-url=https://web.archive.org/web/20230608230244/https://ncbi.nlm.nih.gov/books/NBK56343/ |url-status=live}}{{Update inline|date=May 2022|reason=There is a 2014 update to the report: https://www.ncbi.nlm.nih.gov/books/NBK241444/ (free to access)}} Studies on pet therapy have shown positive effects.{{cite journal |vauthors=Rumayor CB, Thrasher AM |title=Reflections on Recent Research Into Animal-Assisted Interventions in the Military and Beyond |journal=Current Psychiatry Reports |volume=19 |issue=12 |page=110 |date=November 2017 |pmid=29177710 |doi=10.1007/s11920-017-0861-z |s2cid=207338873}}

{{Main|Prognosis of autism}}

There is no evidence of an intervention that removes autism. The degree of characteristics can decrease, occasionally to the extent that people lose their diagnosis of autism;{{cite journal |vauthors=Helt M, Kelley E, Kinsbourne M, Pandey J, Boorstein H, Herbert M, Fein D |date=December 2008 |title=Can children with autism recover? If so, how? |journal=Neuropsychology Review |volume=18 |issue=4 |pages=339–366 |citeseerx=10.1.1.695.2995 |doi=10.1007/s11065-008-9075-9 |pmid=19009353 |s2cid=4317267}}{{cite journal |display-authors=6 |vauthors=Fein D, Barton M, Eigsti IM, Kelley E, Naigles L, Schultz RT, Stevens M, Helt M, Orinstein A, Rosenthal M, Troyb E, Tyson K |date=February 2013 |title=Optimal outcome in individuals with a history of autism |journal=Journal of Child Psychology and Psychiatry, and Allied Disciplines |volume=54 |issue=2 |pages=195–205 |doi=10.1111/jcpp.12037 |pmc=3547539 |pmid=23320807}} this occurs sometimes after intensive interventions{{cite journal |display-authors=6 |vauthors=Orinstein AJ, Helt M, Troyb E, Tyson KE, Barton ML, Eigsti IM, Naigles L, Fein DA |date=May 2014 |title=Intervention for optimal outcome in children and adolescents with a history of autism |journal=Journal of Developmental and Behavioral Pediatrics |volume=35 |issue=4 |pages=247–256 |doi=10.1097/DBP.0000000000000037 |pmc=4487510 |pmid=24799263}} and sometimes not. It is not known how often this outcome happens, with reported rates in unselected samples ranging from 3% to 25%. Although core difficulties tend to persist, characteristics often become less pronounced with age. Acquiring language before age six, having an IQ above 50, and having a marketable skill all predict better outcomes; independent living is unlikely in autistic people with higher support needs.{{cite journal |vauthors=Tidmarsh L, Volkmar FR |date=September 2003 |title=Diagnosis and epidemiology of autism spectrum disorders |journal=Canadian Journal of Psychiatry |volume=48 |issue=8 |pages=517–525 |doi=10.1177/070674370304800803 |pmid=14574827 |doi-access=free |s2cid=38070709}}

Among others, academic Temple Grandin has advised against striving to cure autism, saying that if a cure were found, she would choose to stay the way she is. She wrote, "The skills that [autistic people] bring to the table should be nurtured for their benefit and [for the benefit of] society", adding, "If you totally get rid of autism, you'd have nobody to fix your computer in the future".{{Cite web |title=Temple Grandin to Speak on the Value of Alternative Thinking |url=https://news.callutheran.edu/2024/01/temple-grandin-to-speak-on-the-value-of-alternative-thinking-2/ |access-date=16 June 2024 |website=California Lutheran University |language=en-US}}{{Cite web |title=Two presentations by Temple Grandin offered at MJC |url=https://www.mjc.edu/news/grandin |archive-url=https://web.archive.org/web/20240616214226/https://www.mjc.edu/news/grandin |archive-date=16 June 2024 |website=MJC.edu |publisher=Modesto Junior College}}

The prognosis of autism describes the developmental course, gradual autism development, regressive autism development, differential outcomes, academic performance and employment.

{{Main|Epidemiology of autism}}

The World Health Organization estimates about 1 in 100 children had autism during the period from 2012 to 2021 as that was the average estimate in studies published during that period with a trend of increasing prevalence over time. However, the study's 1% figure may reflect an underestimate of prevalence in low- and middle-income countries.{{cite web |date=30 March 2022 |title=Autism |url=https://www.who.int/news-room/fact-sheets/detail/autism-spectrum-disorders |access-date=8 May 2022 |website=World Health Organization |language=en |archive-date=10 April 2020 |archive-url=https://web.archive.org/web/20200410103835/https://www.who.int/news-room/fact-sheets/detail/autism-spectrum-disorders |url-status=live}} The number of people diagnosed has increased considerably since the 1990s, which may be partly due to increased recognition of autism.{{cite journal |display-authors=6 |vauthors=Russell G, Stapley S, Newlove-Delgado T, Salmon A, White R, Warren F, Pearson A, Ford T |date=August 2021 |title=Time trends in autism diagnosis over 20 years: a UK population-based cohort study |journal=Journal of Child Psychology and Psychiatry, and Allied Disciplines |issn=0021-9630 |eissn=1469-7610 |oclc=01307942 |volume=63 |issue=6 |pages=674–682 |doi=10.1111/jcpp.13505 |pmid=34414570 |quote=The figure starkly illustrates an overall 787% increase in recorded incidence of autism diagnosis over 20 years. |s2cid=237242123 |doi-access=free|hdl=10871/126929 |hdl-access=free}}

While rates of autism are consistent across cultures, they vary greatly by gender, with boys diagnosed far more frequently than girls: 1 in 70 boys, but only 1 in 315 girls at eight years of age.{{cite journal |display-authors=6 |vauthors=Maenner MJ, Shaw KA, Baio J, Washington A, Patrick M, DiRienzo M, Christensen DL, Wiggins LD, Pettygrove S, Andrews JG, Lopez M, Hudson A, Baroud T, Schwenk Y, White T, Rosenberg CR, Lee LC, Harrington RA, Huston M, Hewitt A, Esler A, Hall-Lande J, Poynter JN, Hallas-Muchow L, Constantino JN, Fitzgerald RT, Zahorodny W, Shenouda J, Daniels JL, Warren Z, Vehorn A, Salinas A, Durkin MS, Dietz PM |date=March 2020 |title=Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years - Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2016 |journal=MMWR. Surveillance Summaries |language=en-us |volume=69 |issue=4 |pages=1–12 |doi=10.15585/mmwr.ss6904a1 |pmc=7119644 |pmid=32214087}} Girls, however, are more likely to have associated cognitive disability, suggesting that less obvious forms of autism are likely being missed in girls and women.{{sfn|ICD-11|loc="Females diagnosed with autism spectrum disorder are more frequently diagnosed with co-occurring disorders of intellectual development, suggesting that less severe presentations may go undetected as compared to males"}} Prevalence differences may be a result of gender differences in expression of characteristics, with women and girls with autism showing less atypical behaviors and, therefore, less likely to receive an autism diagnosis.{{cite journal |vauthors=Tsakanikos E, Underwood L, Kravariti E, Bouras N, McCarthy J |title=Gender differences in co-morbid psychopathology and clinical management in adults with autism spectrum disorders |journal=Research in Autism Spectrum Disorders |volume=5 |issue=2 |year=2011 |pages=803–808 |issn=1750-9467 |doi=10.1016/j.rasd.2010.09.009}}

Using DSM-5 criteria, 92% of the children diagnosed per DSM-IV with one of the disorders which is considered part of autism will still meet the diagnostic criteria of autism. However, if both autism and the social (pragmatic) communication disorder categories of DSM-5 are combined, the prevalence of autism is mostly unchanged from the prevalence per the DSM-IV criteria. The best estimate for prevalence of autism is 0.7% or 1 child in 143 children.{{cite book |title=Autism spectrum disorders |vauthors=Hollander E, Hagerman RJ, Fein D |publisher=American Psychiatric Association Publishing |date=30 April 2018 |isbn=978-1-61537-192-1 |edition=First |location=Washington, DC |oclc=1022084798}} Forms of autism with lower support needs, such as Asperger's as well as other developmental disorders, are included in the DSM-5 diagnostic criteria.{{cite journal |vauthors=Baio J, Wiggins L, Christensen DL, et al |title=Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years – Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2014 |journal=MMWR. Surveillance Summaries |volume=67 |issue=6 |pages=1–23 |date=April 2018 |pmid=29701730 |pmc=5919599 |doi=10.15585/mmwr.ss6706a1}} Autism rates were constant between 2014 and 2016 but twice the rate compared to the time period between 2011 and 2014 (1.25 vs 2.47%). A Canadian meta-analysis from 2019 confirmed these effects as the profiles of autistic people became less and less different from the profiles of the general population.{{cite journal |vauthors=Rødgaard EM, Jensen K, Vergnes JN, Soulières I, Mottron L |title=Temporal Changes in Effect Sizes of Studies Comparing Individuals With and Without Autism: A Meta-analysis |journal=JAMA Psychiatry |volume=76 |issue=11 |pages=1124–1132 |date=August 2019 |pmid=31433441 |pmc=6704749 |doi=10.1001/jamapsychiatry.2019.1956}} In the US, the rates for diagnosed autism have been steadily increasing since 2000 when records began being kept.{{cite web |title=CDC estimates 1 in 68 school-aged children have autism; no change from previous estimate |website=CDC Newsroom |url=https://www.cdc.gov/media/releases/2016/p0331-children-autism.html |publisher=CDC |access-date=31 December 2019 |language=en-us |date=31 March 2016 |archive-date=11 October 2019 |archive-url=https://web.archive.org/web/20191011134225/https://www.cdc.gov/media/releases/2016/p0331-children-autism.html |url-status=live}} While it remains unclear whether this trend represents a true rise in incidence, it likely reflects changes in autism diagnostic criteria, improved detection, and increased public awareness of autism.{{cite book |vauthors = Hill AP |date=2014 |veditors=Volkmar FR |chapter=Epidemiology of autism spectrum disorders |title=Handbook of Autism and Pervasive Developmental Disorders. Diagnosis, Development, and Brain Mechanisms |publisher=Wiley |location=New York |volume=1 |pages=57–96 |doi=10.1002/9781118911389 |isbn=978-1-118-91138-9}} In 2012, the NHS estimated that the overall prevalence of autism among adults aged 18 years and over in the UK was 1.1%.{{cite web |display-authors=6 |date=31 January 2012 |title=Estimating the prevalence of autism spectrum conditions in adults: extending the 2007 Adult Psychiatric Morbidity Survey |url=http://www.hscic.gov.uk/catalogue/PUB05061/esti-prev-auti-ext-07-psyc-morb-surv-rep.pdf |archive-url=https://web.archive.org/web/20141230033423/http://www.hscic.gov.uk/catalogue/PUB05061/esti-prev-auti-ext-07-psyc-morb-surv-rep.pdf |archive-date=30 December 2014 |access-date=29 December 2014 |website=The Information Centre for Health and Social Care |publisher=National Health Service, UK |vauthors=Brugha T, Cooper SA, McManus S, Purdon S, Smith J, Scott FJ, Spiers N, Tyrer F}} A 2016 survey in the United States reported a rate of 25 per 1,000 children for autism.{{cite web |date=26 November 2018 |title=Report: Autism Rate Rises to 1 in 40 Children |url=https://www.webmd.com/brain/autism/news/20181126/report-autism-rate-rises-to-1-in-40-children |access-date=26 September 2019 |website=WebMD |vauthors=Mozes A |archive-date=25 September 2019 |archive-url=https://web.archive.org/web/20190925121905/https://www.webmd.com/brain/autism/news/20181126/report-autism-rate-rises-to-1-in-40-children |url-status=live}} Rates of autism are poorly understood in many low- and middle-income countries, which affects the accuracy of global autism prevalence estimates, but it is thought that most autistic people live in low- and middle-income countries.{{cite journal |vauthors=Hahler EM, Elsabbagh M |date=1 March 2015 |title=Autism: A Global Perspective |journal=Current Developmental Disorders Reports |language=en |volume=2 |issue=1 |pages=58–64 |doi=10.1007/s40474-014-0033-3 |issn=2196-2987 |s2cid=73214418 |doi-access=free}}

In 2020, the Centers for Disease Control's Autism and Developmental Disabilities Monitoring (ADDM) Network reported that approximately 1 in 54 children in the United States (1 in 34 boys, and 1 in 144 girls) is diagnosed with autism, based on data collected in 2016.{{cite web |url=https://www.cdc.gov/ncbddd/autism/data.html |title=Data and Statistics on Autism Spectrum Disorder |date=27 March 2020 |website=Centers for Disease Control and Prevention |language=en-us |access-date=19 June 2021 |archive-date=18 April 2014 |archive-url=https://web.archive.org/web/20140418153648/http://www.cdc.gov/ncbddd/autism/data.html |url-status=live}}{{cite journal |vauthors=Maenner MJ, Shaw KA, Bakian AV, Bilder DA, Durkin MS, Esler A, Furnier SM, Hallas L, Hall-Lande J, Hudson A, Hughes MM, Patrick M, Pierce K, Poynter JN, Salinas A, Shenouda J, Vehorn A, Warren Z, Constantino JN, DiRienzo M, Fitzgerald RT, Grzybowski A, Spivey MH, Pettygrove S, Zahorodny W, Ali A, Andrews JG, Baroud T, Gutierrez J, Hewitt A, Lee LC, Lopez M, Mancilla KC, McArthur D, Schwenk YD, Washington A, Williams S, Cogswell ME |display-authors=3 |date=2023 |title=Prevalence and characteristics of autism spectrum disorder among children aged 8 years—Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2020 |journal=MMWR. Surveillance Summaries |language=en-us |volume=72 |issue=2 |pages=1–14 |doi=10.15585/mmwr.ss7202a1 |doi-access=free |issn=1546-0738 |pmid=34855725 |s2cid=257735672 |pmc=8639024}} This estimate is a 10% increase from the 1 in 59 rate in 2014, a 105% increase from the 1 in 110 rate in 2006, and a 176% increase from the 1 in 150 rate in 2000. Diagnostic criteria for autism have changed significantly since the 1980s; for example, U.S. special-education autism classification was introduced in 1994.

In the UK, from 1998 to 2018, the autism diagnoses increased by 787%. This increase is largely attributable to changes in diagnostic practices, referral patterns, availability of services, age at diagnosis, and public awareness,{{cite journal |vauthors=Fombonne E |date=June 2009 |title=Epidemiology of pervasive developmental disorders |journal=Pediatric Research |volume=65 |issue=6 |pages=591–598 |doi=10.1203/PDR.0b013e31819e7203 |pmid=19218885 |doi-access=free}}{{cite journal |vauthors=Wing L, Potter D |year=2002 |title=The epidemiology of autistic spectrum disorders: is the prevalence rising? |journal=Developmental Disabilities Research Reviews |volume=8 |issue=3 |pages=151–161 |doi=10.1002/mrdd.10029 |pmid=12216059}}{{cite journal |vauthors=Gernsbacher MA, Dawson M, Goldsmith HH |date=April 2005 |title=Three Reasons Not to Believe in an Autism Epidemic |journal=Current Directions in Psychological Science |volume=14 |issue=2 |pages=55–58 |doi=10.1111/j.0963-7214.2005.00334.x |pmc=4232964 |pmid=25404790}} particularly among women, though unidentified environmental factors cannot be ruled out.{{cite journal |vauthors=Rutter M |date=January 2005 |title=Incidence of autism spectrum disorders: changes over time and their meaning |journal=Acta Paediatrica |volume=94 |issue=1 |pages=2–15 |doi=10.1111/j.1651-2227.2005.tb01779.x |pmid=15858952 |s2cid=79259285}} The available evidence does not rule out the possibility that autism's true prevalence has increased; a real increase would suggest directing more attention and funding toward psychosocial factors and changing environmental factors instead of continuing to focus on genetics.{{cite journal |vauthors=Szpir M |date=July 2006 |title=Tracing the origins of autism: a spectrum of new studies |journal=Environmental Health Perspectives |volume=114 |issue=7 |pages=A412–A418 |doi=10.1289/ehp.114-a412 |pmc=1513312 |pmid=16835042}} It has been established that vaccination is not a factor for autism likelihood and is not a cause of any increase in autism prevalence rates, if any change in the rate of autism exists at all.

Males have higher likelihood of being diagnosed with autism than females. The sex ratio averages 4.3:1 and is greatly modified by cognitive disability: it may be close to 2:1 with intellectual disability and more than 5.5:1 without. Several theories about the higher prevalence in males have been investigated, but the cause of the difference is unconfirmed;{{cite journal |vauthors=Chaste P, Leboyer M |date=September 2012 |title=Autism risk factors: genes, environment, and gene-environment interactions |journal=Dialogues in Clinical Neuroscience |volume=14 |issue=3 |pages=281–292 |doi=10.31887/DCNS.2012.14.3/pchaste |pmc=3513682 |pmid=23226953}} one theory is that females are underdiagnosed.{{cite journal |vauthors=Schaafsma SM, Pfaff DW |date=August 2014 |title=Etiologies underlying sex differences in Autism Spectrum Disorders |journal=Frontiers in Neuroendocrinology |volume=35 |issue=3 |pages=255–71 |doi=10.1016/j.yfrne.2014.03.006 |pmid=24705124 |s2cid=7636860}}

The likelihood of being autistic is greater with older fathers than with older mothers; two potential explanations are the known increase in the number of mutations in older sperm, and the hypothesis that men marry later if they carry a genetic predisposition and show some signs of autism. Most professionals believe that race, ethnicity, and socioeconomic background do not impact the occurrence of autism.{{cite journal |vauthors=Bertoglio K, Hendren RL |date=March 2009 |title=New developments in autism |journal=Psychiatric Clinics of North America |volume=32 |issue=1 |pages=1–14 |doi=10.1016/j.psc.2008.10.004 |pmid=19248913}}

In 1912, Swiss psychiatrist Paul Bleuler coined the German term Autismus, which was rendered in English as autism. It is a portmanteau of the Greek word autos ("self") and suffix -ismos, denoting an action or state, that conveys the notion of "morbid self-absorption".{{cite web |title=Origin and history of autism |url=https://www.etymonline.com/word/autism |publisher=Etymonline |access-date=}}

{{Main|Societal and cultural aspects of autism}}

File:Greta_Thunberg_in_2022.jpg likened her autism to a "superpower", crediting her success to her focused interests.{{Cite news |title=Greta Thunberg: 'I really see the value of friendship. Apart from the climate, almost nothing else matters' |url=https://www.theguardian.com/environment/ng-interactive/2021/sep/25/greta-thunberg-i-really-see-the-value-of-friendship-apart-from-the-climate-almost-nothing-else-matters |access-date=16 June 2024 |work=The Guardian |date=25 September 2021 |language=en |vauthors=Hattenstone S, Fischer H |archive-url=https://web.archive.org/web/20250406060618/https://www.theguardian.com/environment/ng-interactive/2021/sep/25/greta-thunberg-i-really-see-the-value-of-friendship-apart-from-the-climate-almost-nothing-else-matters |archive-date=6 April 2025}}]]

An autistic culture has emerged, accompanied by the autistic rights and neurodiversity movements, that argues autism should be accepted as a difference to be accommodated instead of cured,{{cite web |date=26 June 2006 |title=Autism Movement Seeks Acceptance, Not Cures |url=https://www.npr.org/templates/story/story.php?storyId=5488463 |access-date=10 November 2015 |publisher=NPR |vauthors=Shapiro J |archive-date=10 May 2019 |archive-url=https://web.archive.org/web/20190510154818/https://www.npr.org/templates/story/story.php?storyId=5488463 |url-status=live}}{{cite magazine |title=Autistic and proud of it |url=https://www.newscientist.com/article/mg18625041-500-autistic-and-proud-of-it/ |access-date=10 November 2015 |publisher=Reed Elsevier |issn=0262-4079 |magazine=New Scientist |vauthors=Trivedi B |archive-date=23 April 2019 |archive-url=https://web.archive.org/web/20190423120053/https://www.newscientist.com/article/mg18625041-500-autistic-and-proud-of-it/ |url-status=live}}{{cite book |title=The Economic World |publisher=Chronicle Publishing Company |year=1917 |location=New York city |page=366}}

{{cite journal |vauthors=Silverman C |year=2008 |title=Fieldwork on another planet: social science perspectives on the autism spectrum |journal=BioSocieties |volume=3 |issue=3 |pages=325–341 |doi=10.1017/S1745855208006236 |s2cid=145379758 |doi-access=free}} although a minority of autistic people might still accept a cure.{{cite web |date=23 March 2022 |title=Results and Analysis of the Autistic Not Weird 2022 Autism Survey - Autistic Not Weird |url=https://autisticnotweird.com/autismsurvey/ |access-date=29 April 2022 |language=en-GB |archive-date=8 June 2023 |archive-url=https://web.archive.org/web/20230608144053/https://autisticnotweird.com/autismsurvey/ |url-status=live}} Worldwide, events related to autism include World Autism Awareness Day, Autism Sunday, Autistic Pride Day, Autreat, and others.{{cite web |title=World Autism Awareness Day, 2 April |url=https://www.un.org/en/events/autismday/ |access-date=17 November 2015 |publisher=United Nations |archive-date=31 March 2018 |archive-url=https://web.archive.org/web/20180331054119/https://www.un.org/en/events/autismday/ |url-status=live}}{{cite web |date=18 June 2015 |title=Autistic Pride Day 2015: A Message to the Autistic Community |url=http://autisticadvocacy.org/2015/06/autistic-pride-day-2015-a-message-to-the-autistic-community/ |access-date=18 November 2015 |vauthors=Bascom J |archive-date=19 November 2015 |archive-url=https://web.archive.org/web/20151119190817/http://autisticadvocacy.org/2015/06/autistic-pride-day-2015-a-message-to-the-autistic-community/ |url-status=live}}{{cite web |year=2010 |title=Autism Sunday – Home |url=http://www.autismsunday.co.uk/ |archive-url=https://web.archive.org/web/20100303043146/http://www.autismsunday.co.uk/ |archive-date=3 March 2010 |access-date=17 November 2015 |website=Autism Sunday}}{{cite web |year=2013 |title=About Autreat |url=http://www.autreat.com/autreat.html |access-date=17 November 2015 |publisher=Autreat.com |archive-date=1 December 2015 |archive-url=https://web.archive.org/web/20151201181250/http://www.autreat.com/autreat.html |url-status=live}}

Social-science scholars study those with autism in hopes to learn more about "autism as a culture, transcultural comparisons ... and research on social movements." Many autistic people have been successful in their fields.{{cite journal |vauthors=Russell G, Kapp SK, Elliott D, Elphick C, Gwernan-Jones R, Owens C |title=Mapping the Autistic Advantage from the Accounts of Adults Diagnosed with Autism: A Qualitative Study |journal=Autism in Adulthood |date=13 April 2019 |volume=1 |issue=2 |pages=124–133 |doi=10.1089/aut.2018.0035 |pmid=31058260 |pmc=6493410 |s2cid=142504027}}

Focused interests are commonly found in autistic people, sometimes leading to hobbies, vast collections, and activism. Environmental activist Greta Thunberg has spoken favorably about her autism diagnosis, saying that autism can be a source of life purpose, as well as forming the basis of careers, hobbies, and friendships.{{Cite web |last=Silberman |first=Steve |date=6 May 2019 |title=Greta Thunberg became a climate activist not in spite of her autism, but because of it |url=https://www.vox.com/first-person/2019/5/6/18531551/greta-thunberg-autism-aspergers |access-date=16 June 2024 |website=Vox |language=en-US}}{{Cite web |last=Ryan |first=Maggie |date=12 April 2024 |title=These 12 Celebrities With Autism Are Opening Up About Life on the Spectrum |url=https://www.sheknows.com/health-and-wellness/slideshow/2992980/celebrities-with-autism/ |access-date=16 June 2024 |website=SheKnows |language=en-US}}

Some autistic people, as well as a growing number of researchers,{{cite journal |vauthors=Pellicano E, den Houting J |date=April 2022 |title=Annual Research Review: Shifting from 'normal science' to neurodiversity in autism science |journal=Journal of Child Psychology and Psychiatry, and Allied Disciplines |volume=63 |issue=4 |pages=381–396 |doi=10.1111/jcpp.13534 |issn=0021-9630 |eissn=1469-7610 |oclc=01307942 |pmc=9298391 |pmid=34730840 |s2cid=241118562}} have advocated a shift in attitudes toward the view that autism is a difference, rather than a disease that ought to be treated or cured.{{cite journal |journal=Disability & Society |year=2007 |volume=22 |issue=7 |pages=761–76 |title='Surplus suffering': differences between organizational understandings of Asperger's syndrome and those people who claim the 'disorder' |vauthors=Clarke J, van Amerom G |doi=10.1080/09687590701659618 |s2cid=145736625}}{{cite journal |journal=Focus Autism Other Dev Disabl |year=2002 |volume=17 |issue=3 |pages=186–91 |title=Is Asperger syndrome necessarily viewed as a disability? |vauthors=Baron-Cohen S |doi=10.1177/10883576020170030801 |s2cid=145629311}} A preliminary, freely readable draft, with slightly different wording in the quoted text, is in: {{cite web |url=http://autismresearchcentre.com/docs/papers/2002_BC_ASDisability.pdf |access-date=2 December 2008 |year=2002 |vauthors=Baron-Cohen S|title=Is Asperger's syndrome necessarily a disability? |publisher=Autism Research Centre |location=Cambridge |archive-url=https://web.archive.org/web/20081217140628/http://autismresearchcentre.com/docs/papers/2002_BC_ASDisability.pdf |archive-date=17 December 2008}} Critics have bemoaned the entrenchment of some of these groups' opinions, and that they speak to a select group of autistic people with limited difficulties.{{cite journal |vauthors=Morgan J |date=1 October 2016 |title=Autism spectrum disorder: difference or disability? |url=https://www.thelancet.com/journals/laneur/article/PIIS1474-4422(16)30002-3/abstract |journal=The Lancet Neurology |language=en |volume=15 |issue=11 |page=1126 |doi=10.1016/S1474-4422(16)30002-3 |issn=1474-4422 |s2cid=54341655}}{{cite news |title=A medical condition or just a difference? The question roils autism community. |language=en-US |newspaper=The Washington Post |url=https://www.washingtonpost.com/national/health-science/a-medical-condition-or-just-a-difference-the-question-roils-autism-community/2019/05/03/87e26f7e-6845-11e9-8985-4cf30147bdca_story.html |access-date=15 October 2021 |issn=0190-8286}}

The neurodiversity movement and the autism rights movement are social movements within the context of disability rights, emphasizing the concept of neurodiversity, which describes the autism spectrum as a result of natural variations in the human brain rather than a disorder to be cured.{{cite news |last=Solomon |first=Andrew |date=25 May 2008 |title=The autism rights movement |url=https://nymag.com/news/features/47225/ |url-status=live |archive-url=https://web.archive.org/web/20080527025140/http://nymag.com/news/features/47225/ |archive-date=27 May 2008 |access-date=27 May 2008 |work=New York Magazine |issn=0028-7369 |vauthors=}} The autism rights movement advocates including greater acceptance of autistic behaviors, therapies that focus on coping skills rather than imitating the behaviors of those without autism,{{cite web |vauthors=Ratner P |title=Should Autism Be Cured or Is "Curing" Offensive? |url=https://bigthink.com/paul-ratner/should-autism-be-cured-or-is-curing-offfensive |website=Big Think |access-date=16 June 2019 |date=10 July 2016}} and the recognition of the autistic community as a minority group.

Autism rights or neurodiversity advocates believe that the autism spectrum is genetic and should be accepted as a natural variation in the human genome. These movements are not without detractors; a common argument against neurodiversity activists is that most of them have relatively low support needs, or are self-diagnosed, and do not represent the views of autistic people with higher support needs.{{cite journal |vauthors=McGee M |date=August 2012 |title=Neurodiversity |journal=Contexts |volume=11 |issue=3 |pages=12–13 |doi=10.1177/1536504212456175 |s2cid=220720495 |doi-access=free}}{{cite web |vauthors=Sarrett J |date=April 2016 |title=Biocertification and Neurodiversity the Role and Implications of Self-Diagnosis in Autistic Communities |url=https://www.researchgate.net/publication/291949788 |access-date=6 March 2022 |website=www.researchgate.net}} Jacquiline den Houting explores this critique, determining that the voices of low-support needs autistics are "some of the most influential within the neurodiversity movement, although admittedly these voices are a minority within the advocacy community"; she suggests this is in part a shortcoming of the wider neurotypical community, referencing nonspeaking self-advocate Amy Sequenzia's writing.{{cite journal |last1=den Houting |first1=J. |date=2019 |title=Neurodiversity: An insider's perspective. |journal=Autism |volume=23 |issue=2 |pages=271–273 |doi=10.1177/1362361318820762 |pmid=30556743 |s2cid=58767898 |doi-access=free}}{{cite book |editor-last=Bascom |editor-first=Julia |last=Sequenzia |first=Amy |date=7 December 2012 |title=Loud Hands: Autistic People, Speaking |publisher=The Autistic Press |pages=159–160 |isbn=978-1-938800-02-3}}{{Undue weight inline|1=Neurodiversity criticism discussion|date=June 2023}} Pier Jaarsma and Stellan Welin make the argument that only autistic people with lower support needs should be included under the neurodiversity banner, as autism with high support needs may rightfully be viewed as a disability.{{cite journal |last1=Jaarsma |first1=Pier |last2=Welin |first2=Stellan |date=1 March 2012 |title=Autism as a Natural Human Variation: Reflections on the Claims of the Neurodiversity Movement |journal=Health Care Analysis |language=en |volume=20 |issue=1 |pages=20–30 |doi=10.1007/s10728-011-0169-9 |pmid=21311979 |s2cid=18618887 |issn=1573-3394 |url=http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-72172}} The concept of neurodiversity is contentious in autism advocacy and research groups and has led to infighting.{{cite journal |last=Morgan |first=Jules |date=1 October 2016 |title=Autism spectrum disorder: difference or disability? |url=https://www.thelancet.com/journals/laneur/article/PIIS1474-4422(16)30002-3/fulltext |journal=The Lancet Neurology |language=English |volume=15 |issue=11 |page=1126 |doi=10.1016/S1474-4422(16)30002-3 |s2cid=54341655 |issn=1474-4422}}

Since 2011, the Autistic Self Advocacy Network has celebrated April as Autism Acceptance Month. In 2021, the Autism Society of America urged organizations to retitle Autism Awareness Day as Autism Acceptance Day, to focus on "more fully integrating those 1 in 54 Americans living with autism into our social fabric".

In 1963, the British National Autistic Society chose a puzzle piece as its logo, due to its view of autistic people as suffering from a "puzzling" condition.{{Cite web |date=2019-04-20 |title=The Autism Puzzle Piece: A symbol that's going to stay or go? |url=https://the-art-of-autism.com/the-autism-puzzle-piece-a-symbol-of-what/ |access-date=2024-11-28 |website=The Art of Autism |language=en-US}}{{cite web |last=Solomon |first=Debra |date=2 May 2018 |title=The History of the Autism Puzzle Piece Ribbon {{!}} Autism Career Coach Queens |url=https://spectrumroadmap.com/the-history-of-the-autism-puzzle-piece-ribbon/ |access-date=10 October 2023 |website=Spectrum Strategies |language=en-US}} The logo, designed by board member Gerald Gasson, consisted of a green and black puzzle piece with four knobs, with a crying child at its center. Other organizations and advocates adopted the puzzle piece as a symbol of autism, including American organization Autism Speaks, which uses a puzzle piece with one knob, two holes, one edge.

In 1999, the Autism Society of America designed the puzzle ribbon (an awareness ribbon patterned with red, yellow, cyan, and blue puzzle pieces) as a symbol of autism awareness.

The puzzle symbol is controversial among autism advocates and rejected by many. It has been criticized as outdated, now that autism is better understood, as well as implying that autistic people are mysterious or incomplete, and for its association with Autism Speaks.{{Cite web |last=Valerie |date=28 March 2022 |title=Why The Puzzle Piece Isn't Used in Autism Acceptance |url=https://www.123shoot.com/nothing-missing-why-the-puzzle-piece-isnt-used-in-autism-acceptance/ |access-date=16 June 2024 |website=Rock Paper Scissors |language=en-US}} The autism rights movement and neurodiversity advocates have criticized Autism Speaks for its view of autism as a disease to be cured.{{cite web |last1=Matthews |first1=Dylan |date=August 31, 2015 |title=We've called autism a disease for decades. We were wrong. |url=https://www.vox.com/2015/8/31/9233295/autism-rights-kanner-asperger |url-status=live |archive-url=https://web.archive.org/web/20190429115212/https://www.vox.com/2015/8/31/9233295/autism-rights-kanner-asperger |archive-date=April 29, 2019 |access-date=June 15, 2019 |website=Vox}}{{Cite news |last=Picciuto |first=Elizabeth |date=February 25, 2015 |title=They Don't Want an Autism Cure |url=http://www.thedailybeast.com/articles/2015/02/25/they-don-t-want-an-autism-cure.html |url-status=live |archive-url=https://web.archive.org/web/20150228201924/http://www.thedailybeast.com/articles/2015/02/25/they-don-t-want-an-autism-cure.html |archive-date=February 28, 2015 |access-date=March 1, 2015 |work=The Daily Beast}}{{cite news |last=Berrington |first=Lucy |date=November 14, 2013 |title=A Reporter's Guide to the Autism Speaks Debacle |url=https://www.psychologytoday.com/gb/blog/aspergers-alive/201311/reporters-guide-the-autism-speaks-debacle |access-date=August 10, 2022 |work=Psychology Today}}

File:National Autistic Society Puzzle Piece logo 1963.webp|National Autistic Society logo, circa 2000

File:Autism awareness ribbon-20051114.png|Autism awareness ribbon, used by Autism Speaks from 2005

File:Autism Speaks Rebrand.png|Current logo of Autism Speaks

In 2004, neurodiversity advocates Amy and Gwen Nelson designed the "rainbow infinity symbol", originally as the logo for their advocacy group Aspies For Freedom. Many adopted the infinity symbol as a symbol for the autism spectrum. The prismatic colors are often associated with the neurodiversity movement in general.{{cite web |last=Morgan |first=Julian |date=11 March 2018 |title=Going Gold For Autism Acceptance |url=https://www.autisticuk.org/post/going-gold-for-autism-acceptance |access-date=10 October 2023 |website=Autistic UK CIC |language=en}}

In 2018, Julian Morgan wrote the article "Light It Up Gold", a response to the "Light It Up Blue" awareness campaign Autism Speaks launched in 2007.{{cite magazine |last=Willingham |first=Emily |title=No Foolin': Forget About Autism Awareness And Lighting Up Blue |url=https://www.forbes.com/sites/emilywillingham/2017/04/01/no-foolin-forget-about-autism-awareness-and-lighting-up-blue/ |access-date=10 October 2023 |magazine=Forbes |language=en}}{{cite web |last=Franco |first=Janelle |date=2014 |url=https://campussuite-storage.s3.amazonaws.com/prod/1558550/996e2c54-539e-11e8-b9a1-0a0344361b00/1954741/f51bb58c-a4c7-11e9-8c86-121ab0aa6810/file/puzzlepieceproject_educational_tool_kit.pdf |title=Puzzle Piece Project and Autism Awareness Month |publisher=Autism Speaks}} Morgan pushed to use gold to symbolize autism, due its chemical symbol Au, from the Latin {{Lang|la|Aurum}}.

File:Autism spectrum infinity awareness symbol.svg|Autism infinity symbol from 2013, featuring a rainbow gradient from left to right

File:Autism golden infinity loop.png | Gold infinity loop, following Julian Morgan's 2018 push to use gold for autism

An autistic pride flag was created in 2005 by Aspies For Freedom for the first Autistic Pride Day, featuring a rainbow infinity symbol on a white background.{{Cite web |last=Advocate |first=Nova Scotia |date=16 March 2019 |title=News release: Neurodiversity flag raising for World Autism Acceptance Day |url=https://nsadvocate.org/2019/03/16/news-release-neurodiversity-flag-raising-for-world-autism-acceptance-day/ |access-date=8 June 2024 |website=Nova Scotia Advocate |language=en-CA}}

As the rainbow infinity on a white background has become increasingly viewed as representative of neurodiversity in general, several designs have been proposed for an autistic-specific flag.{{cite news |last1=Staff |first1=AU-TI Media |title=Autistic Pride Flag: Is it time to choose an official symbol? |url=https://au-ti.com/2023/06/30/autistic-pride-flag-is-it-time-to-choose-an-official-symbol/ |work=AU-TI |date=30 June 2023}} In 2023, the People's History Museum featured a 2015 autistic pride design by Joseph Redford, featuring a rainbow infinity symbol, a green background for being true to one's nature, and a purple background for neurodiversity.{{cite web |last1=Museum |first1=People's History |title=Nothing About Us Without Us |url=https://phm.org.uk/wp-content/uploads/2023/01/3.-Nauwu-Us-Large-Print-guide-14pt-@-Peoples-History-Museum.pdf |website=People's History Museum |access-date=27 June 2024 |date=16 October 2023 |archive-url=https://web.archive.org/web/20250314201055/https://phm.org.uk/wp-content/uploads/2023/01/3.-Nauwu-Us-Large-Print-guide-14pt-@-Peoples-History-Museum.pdf |archive-date=14 March 2025}}

File:Neurodiversity-2013-Flag.png | An autistic/neurodiversity pride flag featuring a rainbow infinity, based on a design from 2013

File:Autistic Pride Flag (purple and green).svg | The 2015 autistic pride flag by Joseph Redford

Families who care for an autistic child face added stress for varying reasons.{{cite book |url={{Google books|4yzqAgAAQBAJ|page=301|plainurl=yes}} |title=Handbook of Autism and Pervasive Developmental Disorders: Volume Two: Assessment, Interventions, and Policy |publisher=John Wiley & Sons |year=2014 |isbn=978-1-118-28220-5 |veditors=Volkmar FR, Paul R, Pelphrey KA, Rogers SJ |edition=4th |volume=2 |location=Hoboken, New Jersey |page=301 |lccn=2013034363 |oclc=946133861 |access-date=1 March 2019}}{{cite journal |vauthors=Aguiar MC, de Pondé MP |date=March 2019 |title=Parenting a child with autism |journal=Jornal Brasileiro de Psiquiatria |language=en |volume=68 |issue=1 |pages=42–47 |doi=10.1590/0047-2085000000223 |issn=0047-2085 |s2cid=165119472 |doi-access=free}} Parents may struggle to understand the diagnosis and to find appropriate care options. They can take a negative view of the diagnosis, and may struggle emotionally.{{cite news |date=29 April 2015 |title=An Alternative-Medicine Believer's Journey Back to Science |newspaper=WIRED |url=https://www.wired.com/2015/04/alternative-medicine-believers-journey-back-science/ |access-date=13 February 2017 |quote=The entire diagnosis and explanation took no more than 45 minutes. 'In the moment of diagnosis, it feels like the death of your hopes and dreams,' Louise [Laidler] says. There's a quiet grief in her voice, even though two decades have passed. 'In a way, it's even harder than a death, because you can't mourn and go on,' she says. 'You have to figure out how to care for your new child.' |vauthors=Levinovitz A}} More than half of parents over age 50 are still living with their child, as about 85% of autistic people have difficulties living independently.{{cite journal |vauthors=Karst JS, Van Hecke AV |date=September 2012 |title=Parent and family impact of autism spectrum disorders: a review and proposed model for intervention evaluation |journal=Clinical Child and Family Psychology Review |volume=15 |issue=3 |pages=247–77 |doi=10.1007/s10567-012-0119-6 |pmid=22869324 |s2cid=19170894}} Some studies also find decreased earnings among parents who care for autistic children.{{cite journal |vauthors=Montes G, Halterman JS |date=April 2008 |title=Association of childhood autism spectrum disorders and loss of family income |url=http://pediatrics.aappublications.org/cgi/content/full/121/4/e821 |journal=Pediatrics |volume=121 |issue=4 |pages=e821–e826 |doi=10.1542/peds.2007-1594 |pmid=18381511 |archive-url=https://web.archive.org/web/20100304071520/http://pediatrics.aappublications.org/cgi/content/full/121/4/e821 |archive-date=4 March 2010 |s2cid=55179}}{{cite journal |vauthors=Montes G, Halterman JS |date=July 2008 |title=Child care problems and employment among families with preschool-aged children with autism in the United States |url=http://pediatrics.aappublications.org/cgi/content/full/122/1/e202 |journal=Pediatrics |volume=122 |issue=1 |pages=e202–e208 |doi=10.1542/peds.2007-3037 |pmid=18595965 |archive-url=https://web.archive.org/web/20091206190622/http://pediatrics.aappublications.org/cgi/content/full/122/1/e202 |archive-date=6 December 2009 |s2cid=22686553}} Siblings of autistic children report greater admiration and less conflict with the autistic sibling than siblings of non-autistic children, like siblings of children with Down syndrome. But they reported lower levels of closeness and intimacy than siblings of children with Down syndrome; siblings of autistic people have a greater risk of negative well-being and poorer sibling relationships as adults.{{cite journal |vauthors=Orsmond GI, Seltzer MM |year=2007 |title=Siblings of individuals with autism spectrum disorders across the life course |url=http://www.waisman.wisc.edu/family/pubs/Autism/2007%20siblings_autism_life-course.pdf |journal=Developmental Disabilities Research Reviews |volume=13 |issue=4 |pages=313–320 |citeseerx=10.1.1.359.7273 |doi=10.1002/mrdd.20171 |pmid=17979200 |archive-url=https://web.archive.org/web/20130530100939/http://www.waisman.wisc.edu/family/pubs/Autism/2007%20siblings_autism_life-course.pdf |archive-date=30 May 2013}}

{{div col|colwidth=35em}}

• Outline of autism
• Animal model of autism
• Autism and memory
• Autism in popular culture
• Autistic art
• Controversies in autism
• Discrimination against autistic people
• Global perceptions of autism
• History of autism
• List of autistic fictional characters
• List of films about autism
• Violence and autism

{{div col end}}

{{Notelist}}

{{Reflist|colwidth=30em}}

• {{cite book |title=Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) |title-link=DSM-5-TR |chapter=Neurodevelopmental Disorders |publisher=American Psychiatric Association |place=Washington, DC |date=18 March 2022 |lccn=2021051782 |isbn=978-0-89042-577-0 |ref={{harvid|DSM-5-TR}}}}
• {{cite encyclopedia |title=6A02 Autism spectrum disorder |date=February 2022 |orig-date=adopted in 2019 |url=https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/437815624 |encyclopedia=International Classification of Diseases 11th Revision (ICD-11) |publisher=World Health Organization |access-date=14 May 2022 |id={{ICD11|6A02|437815624}} |ref={{harvid|ICD-11}}}}

{{Library resources box |onlinebooks=yes}}{{Empty section|date=April 2025}}

• [https://www.who.int/news-room/fact-sheets/detail/autism-spectrum-disorders World Health Organization fact sheet on autism]
• [https://www.autistica.org.uk/what-is-autism/suicide-and-autism Suicide and autism]. Autistica.

{{Medical condition classification and resources

| ICD11 = {{ICD11|6A02}}

| ICD10 = {{ICD10|F84.0}}

| ICD9 = {{ICD9|299.00}}

| OMIM = 209850

| MeSH = D000067877

| Curlie = Health/Mental_Health/Disorders/Neurodevelopmental/Autism_Spectrum

| MedlinePlus = 001526

| eMedicine_mult = {{eMedicine2|ped|180}}

| PatientUK = autism

}}

{{Pervasive developmental disorders}}

{{Autism resources}}

{{Mental and behavioural disorders|selected=neurological}}

{{Digital media use and mental health}}

{{Nonverbal communication}}

{{Subject bar|c=Category:Autism|b=y|q=Autism|d=Q1436063|n=Category:Autism|wikt=autism spectrum}}

{{Authority control}}

Category:Autism spectrum disorders

Category:Developmental psychology

Category:Learning disabilities