functional disorder

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Functional disorders are mostly understood as conditions characterised by:

• persistent and troublesome symptoms
• associated with impairment or disability
• where the pathophysiological basis is related to problems with the functioning and communication of the body systems (as opposed to disease affecting the structure of organs or tissues)

There are many different functional disorder diagnoses that might be given depending on the symptom or syndrome that is most troublesome. There are many examples of symptoms that individuals may experience; some of these include persistent or recurrent pain, fatigue, weakness, shortness of breath or bowel problems. Single symptoms may be assigned a diagnostic label, such as "functional chest pain", "functional constipation" or "functional seizures". Characteristic collections of symptoms might be described as one of the functional somatic syndromes.{{cite journal | vauthors = Barsky AJ, Borus JF | title = Functional somatic syndromes | journal = Annals of Internal Medicine | volume = 130 | issue = 11 | pages = 910–921 | date = June 1999 | pmid = 10375340 | doi = 10.7326/0003-4819-130-11-199906010-00016 | s2cid = 668300 }} A syndrome is a collection of symptoms. Somatic means 'of the body'. Examples of functional somatic syndromes include: irritable bowel syndrome; cyclic vomiting syndrome; some persistent fatigue and chronic pain syndromes, such as fibromyalgia (chronic widespread pain), or chronic pelvic pain; interstitial cystitis; functional neurologic disorder; and multiple chemical sensitivity.{{cn|date=April 2024}}

Most medical specialties define their own functional somatic syndrome, and a patient may end up with several of these diagnoses without understanding how they are connected. There is overlap in symptoms between all the functional disorder diagnoses. For example, it is not uncommon to have a diagnosis of irritable bowel syndrome (IBS) and chronic widespread pain/fibromyalgia.{{cite journal | vauthors = Wessely S, Nimnuan C, Sharpe M | title = Functional somatic syndromes: one or many? | language = English | journal = Lancet | volume = 354 | issue = 9182 | pages = 936–939 | date = September 1999 | pmid = 10489969 | doi = 10.1016/S0140-6736(98)08320-2 | s2cid = 11203982 }} All functional disorders share risk factors and factors that contribute to their persistence. Increasingly researchers and clinicians are recognising the relationships between these syndromes.{{cn|date=February 2024}}

The terminology for functional disorders has been fraught with confusion and controversy, with many different terms used to describe them. Sometimes functional disorders are equated or mistakenly confused with diagnoses like category of "somatoform disorders", "medically unexplained symptoms", "psychogenic symptoms" or "conversion disorders". Many historical terms are now no longer thought of as accurate, and are considered by many to be stigmatising.{{cite journal | vauthors = Barron E, Rotge JY | title = Talking about "psychogenic nonepileptic seizure" is wrong and stigmatizing | journal = Seizure | volume = 71 | pages = 6–7 | date = October 2019 | pmid = 31154287 | doi = 10.1016/j.seizure.2019.05.021 | s2cid = 163168382 | doi-access = free }}

Psychiatric illnesses have historically also been considered as functional disorders in some classification systems, as they often fulfil the criteria above. Whether a given medical condition is termed a functional disorder depends in part on the state of knowledge. Some diseases, such as epilepsy, were historically categorized as functional disorders but are no longer classified that way.{{cn|date=June 2024}}

Functional disorders can affect individuals of all ages, ethnic groups and socioeconomic backgrounds. In clinical populations, functional disorders are common and have been found to present in around one-third of consultations in both specialist practice{{cite journal | vauthors = Nimnuan C, Hotopf M, Wessely S | title = Medically unexplained symptoms: an epidemiological study in seven specialities | journal = Journal of Psychosomatic Research | volume = 51 | issue = 1 | pages = 361–367 | date = July 2001 | pmid = 11448704 | doi = 10.1016/S0022-3999(01)00223-9 }} and primary care.{{cite journal | vauthors = Haller H, Cramer H, Lauche R, Dobos G | title = Somatoform disorders and medically unexplained symptoms in primary care | journal = Deutsches Ärzteblatt International | volume = 112 | issue = 16 | pages = 279–287 | date = April 2015 | pmid = 25939319 | pmc = 4442550 | doi = 10.3238/arztebl.2015.0279 }} Chronic courses of disorders are common and are associated with high disability, health-care usage and social costs.{{cite journal | vauthors = Konnopka A, Schaefert R, Heinrich S, Kaufmann C, Luppa M, Herzog W, König HH | title = Economics of medically unexplained symptoms: a systematic review of the literature | language = english | journal = Psychotherapy and Psychosomatics | volume = 81 | issue = 5 | pages = 265–275 | date = 2012 | pmid = 22832397 | doi = 10.1159/000337349 | s2cid = 8043003 | url = http://archiv.ub.uni-heidelberg.de/volltextserver/17786/1/PPS2012081005265.pdf }}

Rates differ in the clinical population compared with the general population, and will vary depending on the criteria used to make the diagnosis. For example, irritable bowel syndrome is thought to affect 4.1%,{{cite journal | vauthors = Sperber AD, Bangdiwala SI, Drossman DA, Ghoshal UC, Simren M, Tack J, Whitehead WE, Dumitrascu DL, Fang X, Fukudo S, Kellow J, Okeke E, Quigley EM, Schmulson M, Whorwell P, Archampong T, Adibi P, Andresen V, Benninga MA, Bonaz B, Bor S, Fernandez LB, Choi SC, Corazziari ES, Francisconi C, Hani A, Lazebnik L, Lee YY, Mulak A, Rahman MM, Santos J, Setshedi M, Syam AF, Vanner S, Wong RK, Lopez-Colombo A, Costa V, Dickman R, Kanazawa M, Keshteli AH, Khatun R, Maleki I, Poitras P, Pratap N, Stefanyuk O, Thomson S, Zeevenhooven J, Palsson OS | display-authors = 6 | title = Worldwide Prevalence and Burden of Functional Gastrointestinal Disorders, Results of Rome Foundation Global Study | journal = Gastroenterology | volume = 160 | issue = 1 | pages = 99–114.e3 | date = January 2021 | pmid = 32294476 | doi = 10.1053/j.gastro.2020.04.014 | s2cid = 215793263 | doi-access = free }} and fibromyalgia 0.2–11.4% of the global population.{{cite journal | vauthors = Marques AP, Santo AS, Berssaneti AA, Matsutani LA, Yuan SL | title = Prevalence of fibromyalgia: literature review update | journal = Revista Brasileira de Reumatologia | volume = 57 | issue = 4 | pages = 356–363 | date = 2017-07-01 | pmid = 28743363 | doi = 10.1016/j.rbre.2017.01.005 | doi-access = free }}

A recent large study carried out on population samples in Denmark showed the following: In total, 16.3% of adults reported symptoms fulfilling the criteria for at least one Functional Somatic Syndrome, and 16.1% fulfilled criteria for Bodily Distress Syndrome.{{cite journal | vauthors = Petersen MW, Schröder A, Jørgensen T, Ørnbøl E, Dantoft TM, Eliasen M, Carstensen TW, Falgaard Eplov L, Fink P | display-authors = 6 | title = Prevalence of functional somatic syndromes and bodily distress syndrome in the Danish population: the DanFunD study | journal = Scandinavian Journal of Public Health | volume = 48 | issue = 5 | pages = 567–576 | date = July 2020 | pmid = 31409218 | doi = 10.1177/1403494819868592 | s2cid = 199572511 }}

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The diagnosis of functional disorders is usually made in the healthcare setting most often by a doctor — this could be a primary care physician or family doctor, hospital physician or specialist in the area of psychosomatic medicine or a consultant-liaison psychiatrist. The primary care physician or family doctor will generally play an important role in coordinating treatment with a secondary care clinician if necessary.

The diagnosis is essentially clinical, whereby the clinician undertakes a thorough medical and mental health history and physical examination. Diagnosis should be based on the nature of the presenting symptoms, and is a "rule in" as opposed to "rule out" diagnosis — this means it is based on the presence of positive symptoms and signs that follow a characteristic pattern. There is usually a process of clinical reasoning to reach this point and assessment might require several visits, ideally with the same doctor.

In the clinical setting, there are no laboratory or imaging tests that can consistently be used to diagnose the conditions; however, as is the case with all diagnoses, often additional diagnostic tests (such as blood tests, or diagnostic imaging) will be undertaken to consider the presence of underlying disease. There are however diagnostic criteria that can be used to help a doctor assess whether an individual is likely to suffer from a particular functional syndrome. These are usually based on the presence or absence of characteristic clinical signs and symptoms. Self-report questionnaires may also be useful.

There has been a tradition of a separate diagnostic classification systems for "somatic" and "mental" disorder classifications. Currently, the 11th version of the International Classification System of Diseases (ICD-11) has specific diagnostic criteria for certain disorders which would be considered by many clinicians to be functional somatic disorders, such as IBS or chronic widespread pain/fibromyalgia, and dissociative neurological symptom disorder.{{Cite web |title=ICD-11 for Mortality and Morbidity Statistics |url=https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/767044268 |access-date=2022-09-07 |website=icd.who.int}}

In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) the older term somatoform (DSM-IV) has been replaced by somatic symptom disorder, which is a disorder characterised by persistent somatic (physical) symptoms, and associated psychological problems to the degree that it interferes with daily functioning and causes distress. (APA, 2022). Bodily distress disorder is a related term in the ICD-11.

Somatic symptom disorder and bodily distress disorder have significant overlap with functional disorders and are often assigned if someone would benefit from psychological therapies addressing psychological or behavioural factors which contribute to the persistence of symptoms. However, people with symptoms partly explained by structural disease (for example, cancer) may also meet the criteria for diagnosis of functional disorders, somatic symptom disorder and bodily distress disorder.{{cite journal | vauthors = Löwe B, Levenson J, Depping M, Hüsing P, Kohlmann S, Lehmann M, Shedden-Mora M, Toussaint A, Uhlenbusch N, Weigel A | display-authors = 6 | title = Somatic symptom disorder: a scoping review on the empirical evidence of a new diagnosis | journal = Psychological Medicine | volume = 52 | issue = 4 | pages = 632–648 | date = November 2021 | pmid = 34776017 | pmc = 8961337 | doi = 10.1017/S0033291721004177 }}

It is not unusual for a functional disorder to coexist with another diagnosis (for example, functional seizures can coexist with epilepsy,{{cite journal | vauthors = LaFrance WC, Reuber M, Goldstein LH | title = Management of psychogenic nonepileptic seizures | journal = Epilepsia | volume = 54 | issue = Suppl 1 | pages = 53–67 | date = March 2013 | pmid = 23458467 | doi = 10.1111/epi.12106 | s2cid = 205115146 | doi-access = free }} or irritable bowel syndrome with inflammatory bowel disease.{{cite journal | vauthors = Fairbrass KM, Costantino SJ, Gracie DJ, Ford AC | title = Prevalence of irritable bowel syndrome-type symptoms in patients with inflammatory bowel disease in remission: a systematic review and meta-analysis | journal = The Lancet. Gastroenterology & Hepatology | volume = 5 | issue = 12 | pages = 1053–1062 | date = December 2020 | pmid = 33010814 | doi = 10.1016/S2468-1253(20)30300-9 | s2cid = 222154523 | url = https://eprints.whiterose.ac.uk/166988/3/thelancetgastrohep-D-20-00837R1%20clean%20with%20Endnote%20%281%29.pdf }} This is important to recognise as additional treatment approaches might be indicated in order that the patient achieves adequate relief from their symptoms.

The diagnostic process is considered an important step in order for treatment to move forward successfully. When healthcare professionals are giving a diagnosis and carrying out treatment, it is important to communicate openly and honestly and not to fall into the trap of dualistic concepts – that is "either mental or physical" thinking; or attempt to "reattribute" symptoms to a predominantly psychosocial cause.{{cite journal | vauthors = Gask L, Dowrick C, Salmon P, Peters S, Morriss R | title = Reattribution reconsidered: narrative review and reflections on an educational intervention for medically unexplained symptoms in primary care settings | journal = Journal of Psychosomatic Research | volume = 71 | issue = 5 | pages = 325–334 | date = November 2011 | pmid = 21999976 | doi = 10.1016/j.jpsychores.2011.05.008 }} It often important to recognise the need to cease unnecessary additional diagnostic testing if a clear diagnosis has been established .{{Cite book | vauthors = Pall M | doi = 10.4324/9780367806767 |title=Explaining Unexplained Illnesses |date=2013-04-25 |publisher=CRC Press |isbn=978-0-367-80676-7}}

Explanatory models that support our understanding of functional disorders take into account the multiple factors involved in symptom development. A personalised, tailored approach is usually needed in order to consider the factors which relate to that individual's biomedical, psychological, social, and material environment.{{cite journal | vauthors = Cathébras P | title = Patient-Centered Medicine: A Necessary Condition for the Management of Functional Somatic Syndromes and Bodily Distress | journal = Frontiers in Medicine | volume = 8 | pages = 585495 | date = 2021-04-27 | pmid = 33987188 | pmc = 8110699 | doi = 10.3389/fmed.2021.585495 | doi-access = free }}

More recent functional neuroimaging studies have suggested malfunctioning of neural circuits involved in stress processing, emotional regulation, self-agency, interoception, and sensorimotor integration.{{Cite journal |last1=Aybek |first1=Selma |last2=Perez |first2=David L. |date=2022-01-24 |title=Diagnosis and management of functional neurological disorder |url=https://pubmed.ncbi.nlm.nih.gov/35074803 |journal=BMJ (Clinical Research Ed.) |volume=376 |pages=o64 |doi=10.1136/bmj.o64 |issn=1756-1833 |pmid=35074803|s2cid=246210869 }} A recent article in Scientific American proposed that important brain structures suspected in the pathophysiology of functional neurological disorder include increased activity of the amygdala and decreased activity within the right temporoparietal junction.{{Cite web |last=L'Erario |first=Z. Paige |title=New Research Points to Causes for Brain Disorders with No Obvious Injury |url=https://www.scientificamerican.com/article/new-research-points-to-causes-for-brain-disorders-with-no-obvious-injury/ |access-date=2023-05-20 |website=Scientific American |language=en}}

Healthcare professionals might find it useful to consider three main categories of factors: predisposing, precipitating, and perpetuating (maintaining) factors.

These are factors that make the person more vulnerable to the onset of a functional disorder; and include biological, psychological and social factors. Like all health conditions, some people are probably predisposed to develop functional disorders due to their genetic make-up. However, no single genes have been identified that are associated with functional disorders. Epigenetic mechanisms (mechanisms that affect interaction of genes with their environment) are likely to be important, and have been studied in relation to the hypothalamic–pituitary–adrenal axis.{{cite journal | vauthors = Tak LM, Cleare AJ, Ormel J, Manoharan A, Kok IC, Wessely S, Rosmalen JG | title = Meta-analysis and meta-regression of hypothalamic-pituitary-adrenal axis activity in functional somatic disorders | journal = Biological Psychology | volume = 87 | issue = 2 | pages = 183–194 | date = May 2011 | pmid = 21315796 | doi = 10.1016/j.biopsycho.2011.02.002 | s2cid = 206108463 }} Other predisposing factors include current or prior somatic/physical illness or injury, and endocrine, immunological or microbial factors.{{cite journal | vauthors = Löwe B, Andresen V, Van den Bergh O, Huber TB, von dem Knesebeck O, Lohse AW, Nestoriuc Y, Schneider G, Schneider SW, Schramm C, Ständer S, Vettorazzi E, Zapf A, Shedden-Mora M, Toussaint A | display-authors = 6 | title = Persistent SOMAtic symptoms ACROSS diseases - from risk factors to modification: scientific framework and overarching protocol of the interdisciplinary SOMACROSS research unit (RU 5211) | journal = BMJ Open | volume = 12 | issue = 1 | pages = e057596 | date = January 2022 | pmid = 35063961 | pmc = 8785206 | doi = 10.1136/bmjopen-2021-057596 }}

Functional disorders are diagnosed more frequently in female patients.{{cite journal | vauthors = Kingma EM, de Jonge P, Ormel J, Rosmalen JG | title = Predictors of a functional somatic syndrome diagnosis in patients with persistent functional somatic symptoms | journal = International Journal of Behavioral Medicine | volume = 20 | issue = 2 | pages = 206–212 | date = June 2013 | pmid = 22836483 | doi = 10.1007/s12529-012-9251-4 | s2cid = 30177131 }} Medical bias possibly contributes to the sex differences in diagnosis: women are more likely to be diagnosed than men with a functional disorder by doctors.{{cite journal | vauthors = Claréus B, Renström EA | title = Physicians' gender bias in the diagnostic assessment of medically unexplained symptoms and its effect on patient-physician relations | journal = Scandinavian Journal of Psychology | volume = 60 | issue = 4 | pages = 338–347 | date = August 2019 | pmid = 31124165 | pmc = 6851885 | doi = 10.1111/sjop.12545 }}

People with functional disorders also have higher rates of pre-existing mental and physical health conditions, including depression and anxiety disorders,{{cite journal | vauthors = Garakani A, Win T, Virk S, Gupta S, Kaplan D, Masand PS | title = Comorbidity of irritable bowel syndrome in psychiatric patients: a review | journal = American Journal of Therapeutics | volume = 10 | issue = 1 | pages = 61–67 | date = January 2003 | pmid = 12522523 | doi = 10.1097/00045391-200301000-00014 }} Post-traumatic stress disorder,{{cite journal | vauthors = Cohen H, Neumann L, Haiman Y, Matar MA, Press J, Buskila D | title = Prevalence of post-traumatic stress disorder in fibromyalgia patients: overlapping syndromes or post-traumatic fibromyalgia syndrome? | journal = Seminars in Arthritis and Rheumatism | volume = 32 | issue = 1 | pages = 38–50 | date = August 2002 | pmid = 12219319 | doi = 10.1053/sarh.2002.33719 }} multiple sclerosis and epilepsy.{{cite journal | vauthors = Stone J, Carson A, Duncan R, Roberts R, Coleman R, Warlow C, Murray G, Pelosi A, Cavanagh J, Matthews K, Goldbeck R, Sharpe M | display-authors = 6 | title = Which neurological diseases are most likely to be associated with "symptoms unexplained by organic disease" | journal = Journal of Neurology | volume = 259 | issue = 1 | pages = 33–38 | date = January 2012 | pmid = 21674198 | doi = 10.1007/s00415-011-6111-0 | s2cid = 20306076 }} Personality style has been suggested as a risk factor in the development of functional disorders but the effect of any individual personality trait is variable and weak.{{cite journal | vauthors = Macina C, Bendel R, Walter M, Wrege JS | title = Somatization and Somatic Symptom Disorder and its overlap with dimensionally measured personality pathology: A systematic review | journal = Journal of Psychosomatic Research | volume = 151 | pages = 110646 | date = December 2021 | pmid = 34715494 | doi = 10.1016/j.jpsychores.2021.110646 | s2cid = 239529626 | doi-access = free }}{{cite journal | vauthors = Kato K, Sullivan PF, Evengård B, Pedersen NL | title = Premorbid predictors of chronic fatigue | journal = Archives of General Psychiatry | volume = 63 | issue = 11 | pages = 1267–1272 | date = November 2006 | pmid = 17088507 | doi = 10.1001/archpsyc.63.11.1267 | doi-access = free }} Alexithymia (difficulties recognising and naming emotions) has been widely studied in patients with functional disorders and is sometimes addressed as part of treatment.{{cite journal | vauthors = Porcelli P, Bagby RM, Taylor GJ, De Carne M, Leandro G, Todarello O | title = Alexithymia as predictor of treatment outcome in patients with functional gastrointestinal disorders | journal = Psychosomatic Medicine | volume = 65 | issue = 5 | pages = 911–918 | date = September 2003 | pmid = 14508040 | doi = 10.1097/01.psy.0000089064.13681.3b | s2cid = 24284532 }} Migration, cultural and family understanding of illness, are also factors that influence the chance of an individual developing a functional disorder.{{cite journal | vauthors = Isaac M, Janca A, Burke KC, Costa e Silva JA, Acuda SW, Altamura AC, Burke JD, Chandrashekar CR, Miranda CT, Tacchini G | display-authors = 6 | title = Medically unexplained somatic symptoms in different cultures. A preliminary report from phase I of the World Health Organization International Study of Somatoform Disorders | journal = Psychotherapy and Psychosomatics | volume = 64 | issue = 2 | pages = 88–93 | date = 1995 | pmid = 8559958 | doi = 10.1159/000288996 }} Being exposed to illness in the family while growing up or having parents who are healthcare professionals are sometimes considered risk factors. Adverse childhood experiences and traumatic experiences of all kinds are known important risk factors.{{cite journal | vauthors = Bradford K, Shih W, Videlock EJ, Presson AP, Naliboff BD, Mayer EA, Chang L | title = Association between early adverse life events and irritable bowel syndrome | journal = Clinical Gastroenterology and Hepatology | volume = 10 | issue = 4 | pages = 385–390.e3 | date = April 2012 | pmid = 22178460 | pmc = 3311761 | doi = 10.1016/j.cgh.2011.12.018 }}{{cite journal | vauthors = Ludwig L, Pasman JA, Nicholson T, Aybek S, David AS, Tuck S, Kanaan RA, Roelofs K, Carson A, Stone J | display-authors = 6 | title = Stressful life events and maltreatment in conversion (functional neurological) disorder: systematic review and meta-analysis of case-control studies | journal = The Lancet. Psychiatry | volume = 5 | issue = 4 | pages = 307–320 | date = April 2018 | pmid = 29526521 | doi = 10.1016/S2215-0366(18)30051-8 | url = https://discovery.ucl.ac.uk/id/eprint/10074178/ | hdl = 20.500.11820/48a37695-e67f-4614-a2ee-01a284e51988 | hdl-access = free }} Newer hypotheses have suggested minority stressors may play a role in the development of functional disorders in marginalized communities.{{Cite journal |last1=Lerario |first1=Mackenzie P. |last2=Rosendale |first2=Nicole |last3=Waugh |first3=Jeff L. |last4=Turban |first4=Jack |last5=Maschi |first5=Tina |date=2023-04-21 |title=Functional Neurological Disorder Among Sexual and Gender Minority People |url=https://www.sciencedirect.com/science/article/pii/S0733861923000142 |journal=Neurologic Clinics |volume=41 |issue=4 |pages=759–781 |language=en |doi=10.1016/j.ncl.2023.02.010 |pmid=37775203 |s2cid=258291244 |issn=0733-8619|url-access=subscription }}{{Cite journal |last1=Lerario |first1=Mackenzie |last2=Fusunyan |first2=Mark |last3=Stave |first3=Christopher |last4=Waugh |first4=Jeffrey |last5=Wilkinson-Smith |first5=Alison |last6=Roldan |first6=Valeria |last7=Keuroghlian |first7=Alex |last8=Turban |first8=Jack |last9=Perez |first9=David |last10=Maschi |first10=Tina |last11=Rosendale |first11=Nicole |date=2023-04-25 |title=A Scoping Review of Functional Neurological Disorder in Sexual and Gender Minority People |id= P1-12.004 |journal=Neurology |volume=100 |issue=17 Supplement 2 |url=http://www.neurology.org/lookup/doi/10.1212/WNL.0000000000202627 |publisher=Lippincott Williams & Wilkins |at=2534 |doi=10.1212/WNL.0000000000202627|s2cid=258410917 |url-access=subscription }}

These are the factors that for some patients appear to trigger the onset of a functional disorder. Typically, these involve either an acute cause of physical or emotional stress, for example an operation, a viral illness, a car accident, a sudden bereavement, or a period of intense and prolonged overload of chronic stressors (for example relationship difficulties, job or financial stress, or caring responsibilities). Not all affected individuals will be able to identify obvious precipitating factors and some functional disorders develop gradually over time.

These are the factors that contribute to the development of functional disorder as a persistent condition and maintaining symptoms. These can include the condition of the physiological systems including the immune and neuroimmune systems, the endocrine system, the musculoskeletal system, the sleep-wake cycle, the brain and nervous system, the person's thoughts and experience, their experience of the body, social situation and environment. All these layers interact with each other. Illness mechanisms are important therapeutically as they are seen as potential targets of treatment.{{cite journal | vauthors = Kozlowska K | title = Functional somatic symptoms in childhood and adolescence | journal = Current Opinion in Psychiatry | volume = 26 | issue = 5 | pages = 485–492 | date = September 2013 | pmid = 23867659 | doi = 10.1097/yco.0b013e3283642ca0 | s2cid = 43084699 }}

The exact illness mechanisms that are responsible for maintaining an individual's functional disorder should be considered on an individual basis. However, various models have been suggested to account for how symptoms develop and continue. For some people there seems to be a process of central-sensitisation,{{cite journal | vauthors = Bourke JH, Langford RM, White PD | title = The common link between functional somatic syndromes may be central sensitisation | journal = Journal of Psychosomatic Research | volume = 78 | issue = 3 | pages = 228–236 | date = March 2015 | pmid = 25598410 | doi = 10.1016/j.jpsychores.2015.01.003 }} chronic low grade inflammation{{cite journal | vauthors = Lacourt TE, Vichaya EG, Chiu GS, Dantzer R, Heijnen CJ | title = The High Costs of Low-Grade Inflammation: Persistent Fatigue as a Consequence of Reduced Cellular-Energy Availability and Non-adaptive Energy Expenditure | journal = Frontiers in Behavioral Neuroscience | volume = 12 | pages = 78 | date = 2018-04-26 | pmid = 29755330 | doi = 10.3389/fnbeh.2018.00078 | pmc = 5932180 | doi-access = free }} or altered stress reactivity mediated through the hypothalamic-pituitary-adrenal (HPA) axis (Fischer et al., 2022). For some people attentional mechanisms are likely to be important.{{cite journal | vauthors = Barsky AJ, Goodson JD, Lane RS, Cleary PD | title = The amplification of somatic symptoms | journal = Psychosomatic Medicine | volume = 50 | issue = 5 | pages = 510–519 | date = September 1988 | pmid = 3186894 | doi = 10.1097/00006842-198809000-00007 | s2cid = 29282201 }} Commonly, illness-perceptions or behaviours and expectations (Henningsen, Van den Bergh et al. 2018 ) contribute to maintaining an impaired physiological condition.

Perpetuating illness mechanisms are often conceptualized as "vicious cycles", which highlights the non-linear patterns of causality characteristic of these disorders.{{cite journal | vauthors = Brazier DK, Venning HE | title = Conversion disorders in adolescents: a practical approach to rehabilitation | journal = British Journal of Rheumatology | volume = 36 | issue = 5 | pages = 594–598 | date = May 1997 | pmid = 9189063 | doi = 10.1093/rheumatology/36.5.594 | doi-access = free }} Other people adopt a pattern of trying to achieve a lot on "good days" which results in exhaustion for days following and a flare up of symptoms, which has led to various energy management tools being used in the patient community, such as "Spoon Theory."{{Cite news |date=2021-11-16 |title=What Is the Spoon Theory Metaphor for Chronic Illness? |language=en-US |work=Cleveland Clinic |url=https://health.clevelandclinic.org/spoon-theory-chronic-illness/ |access-date=2022-09-07}}

Depression, PTSD, sleep disorders, and anxiety disorders can also perpetuate functional disorders and should be identified and treated where they are present. Side effects or withdrawal effects of medication often need to be considered. Iatrogenic factors such as lack of a clear diagnosis, not feeling believed or not taken seriously by a healthcare professional, multiple (invasive) diagnostic procedures, ineffective treatments and not getting an explanation for symptoms can increase worry and unhelpful illness behaviours. Stigmatising medical attitudes and unnecessary medical interventions (tests, surgeries or drugs) can also cause harm and worsen symptoms.{{cite journal | vauthors = Ashe LM | title = From iatrogenic harm to iatrogenic violence: corruption and the end of medicine | journal = Anthropology & Medicine | volume = 28 | issue = 2 | pages = 255–275 | date = June 2021 | pmid = 34355977 | doi = 10.1080/13648470.2021.1932415 | s2cid = 236934489 }}

Functional disorders can be treated successfully and are considered reversible conditions. Treatment strategies should integrate biological, psychological and social perspectives. The body of research around evidence-based treatment in functional disorders is growing.{{Cite book | vauthors = Henningsen P, Zipfel S, Sattel H, Creed F |url=http://worldcat.org/oclc/1187867360 |title=Management of Functional Somatic Syndromes and Bodily Distress |oclc=1187867360}}

With regard to self-management, there are many basic things that can be done to optimise recovery. Learning about and understanding the condition is helpful in itself.{{cite journal | vauthors = van Gils A, Schoevers RA, Bonvanie IJ, Gelauff JM, Roest AM, Rosmalen JG | title = Self-Help for Medically Unexplained Symptoms: A Systematic Review and Meta-Analysis | journal = Psychosomatic Medicine | volume = 78 | issue = 6 | pages = 728–739 | date = July 2016 | pmid = 27187850 | doi = 10.1097/psy.0000000000000325 | s2cid = 23734980 | url = https://pure.rug.nl/ws/files/773040054/self_help_for_medically_unexplained_symptoms_a.11.pdf }} Many people are able to use bodily complaints as a signal to slow down and reassess their balance between exertion and recovery. Bodily complaints can be used as a signal to begin incorporating stress reduction and balanced lifestyle measures (routine, regular activity and relaxation, diet, social engagement) that can help reduce symptoms and are central to improving quality of life. Mindfulness practice can be helpful for some people.{{cite journal | vauthors = Lakhan SE, Schofield KL | title = Mindfulness-based therapies in the treatment of somatization disorders: a systematic review and meta-analysis | journal = PLOS ONE | volume = 8 | issue = 8 | pages = e71834 | date = 2013-08-26 | pmid = 23990997 | doi = 10.1371/journal.pone.0071834 | pmc = 3753315 | bibcode = 2013PLoSO...871834L | doi-access = free }} Family members or friends can also be helpful in supporting recovery.

Most affected people benefit from support and encouragement in this process, ideally through a multi-disciplinary team with expertise in treating functional disorders. Family members or friends may also be helpful in supporting recovery. The aim of treatment overall is to first create the conditions necessary for recovery, and then plan a programme of rehabilitation to re-train mind-body connections making use of the body's ability to change. Particular strategies can be taught to manage bowel symptoms, pain or seizures. Though medication alone should not be considered curative in functional disorders, medication to reduce symptoms might be indicated in some instances, for example where mood or pain is a significant issue, preventing adequate engagement in rehabilitation. It is important to address accompanying factors such as sleep disorders, pain, depression and anxiety, and concentration difficulties.

Physiotherapy may be relevant for exercise and activation programs, or when weakness or pain is a problem.{{cite journal | vauthors = Nielsen G, Stone J, Matthews A, Brown M, Sparkes C, Farmer R, Masterton L, Duncan L, Winters A, Daniell L, Lumsden C, Carson A, David AS, Edwards M | display-authors = 6 | title = Physiotherapy for functional motor disorders: a consensus recommendation | journal = Journal of Neurology, Neurosurgery, and Psychiatry | volume = 86 | issue = 10 | pages = 1113–1119 | date = October 2015 | pmid = 25433033 | doi = 10.1136/jnnp-2014-309255 | pmc = 4602268 }} Psychotherapy might be helpful to explore a pattern of thoughts, actions and behaviours that could be driving a negative cycle – for example tackling illness expectations or preoccupations about symptoms.{{Cite journal | vauthors = Hennemann S, Böhme K, Kleinstäuber M, Baumeister H, Küchler AM, Ebert DD |date=2022 |title=Supplemental Material for Internet-Based CBT for Somatic Symptom Distress (iSOMA) in Emerging Adults: A Randomized Controlled Trial |url=http://dx.doi.org/10.1037/ccp0000707.supp |journal=Journal of Consulting and Clinical Psychology |doi=10.1037/ccp0000707.supp |s2cid=246769680 |issn=0022-006X|url-access=subscription }} Some existing evidence-based treatments include cognitive behavioural therapy (CBT) for functional neurological disorder;{{cite journal | vauthors = Goldstein LH, Robinson EJ, Chalder T, Reuber M, Medford N, Stone J, Carson A, Moore M, Landau S | display-authors = 6 | title = Six-month outcomes of the CODES randomised controlled trial of cognitive behavioural therapy for dissociative seizures: A secondary analysis | journal = Seizure | volume = 96 | pages = 128–136 | date = March 2022 | pmid = 35228117 | doi = 10.1016/j.seizure.2022.01.016 | pmc = 8970049 }} physiotherapy for functional motor symptoms,{{Cite journal |last1=Vassilopoulos |first1=Areti |last2=Mohammad |first2=Shekeeb |last3=Dure |first3=Leon |last4=Kozlowska |first4=Kasia |last5=Fobian |first5=Aaron D. |date=2022 |title=Treatment Approaches for Functional Neurological Disorders in Children |journal=Current Treatment Options in Neurology |volume=24 |issue=2 |pages=77–97 |doi=10.1007/s11940-022-00708-5 |issn=1092-8480 |pmc=8958484 |pmid=35370394}} and dietary modification or gut targeting agents for irritable bowel syndrome.{{cite book | chapter = Irritable Bowel Syndrome |date= October 2020 | doi = 10.1891/9780826185235.0008o | title = Pediatric Practice Guidelines |place=New York, NY |publisher=Springer Publishing Company |isbn= 978-0-8261-6869-6 |s2cid= 70708220 }}

Despite some progress in the last decade, people with functional disorders continue to suffer subtle and overt forms of discrimination by clinicians, researchers and the public. Stigma is a common experience for individuals who present with functional symptoms and is often driven by historical narratives and factual inaccuracies. Given that functional disorders do not usually have specific biomarkers or findings on structural imaging that are typically undertaken in routine clinical practice, this leads to potential for symptoms to be misunderstood, invalidated, or dismissed, leading to adverse experiences when individuals are seeking help.{{cite journal | vauthors = Looper KJ, Kirmayer LJ | title = Perceived stigma in functional somatic syndromes and comparable medical conditions | journal = Journal of Psychosomatic Research | volume = 57 | issue = 4 | pages = 373–378 | date = October 2004 | pmid = 15518673 | doi = 10.1016/s0022-3999(04)00447-7 | url = https://escholarship.mcgill.ca/concern/theses/1544br23x }}

Part of this stigma is also driven by theories around "mind body dualism", which frequently surfaces as an area of importance for patients, researchers and clinicians in the realm of functional disorders. Artificial separation of the mind/brain/body (for example the use of phrases such as; "physical versus psychological" or "organic versus non-organic") furthers misunderstanding and misconceptions around these disorders, and only serves to hinder progress in scientific domain and for patients seeking treatment. Some patient groups have fought to have their illnesses not classified as functional disorders, because in some insurance based health-care systems these have attracted lower insurance payments.{{cite journal | vauthors = Dumit J | title = Illnesses you have to fight to get: facts as forces in uncertain, emergent illnesses | journal = Social Science & Medicine | volume = 62 | issue = 3 | pages = 577–590 | date = February 2006 | pmid = 16085344 | doi = 10.1016/j.socscimed.2005.06.018 }} Current research is moving away from dualistic theories, and recognising the importance of the whole person, both mind and body, in diagnosis and treatment of these conditions.

People with functional disorders frequently describe experiences of doubt, blame, and of being seen as less 'genuine' than those with other disorders. Some clinicians perceive those individuals with functional disorders are imagining their symptoms, are malingering, or doubt the level of voluntary control they have over their symptoms. As a result, individuals with these disorders often wait long periods of time to be seen by specialists and receive appropriate treatment.{{cite journal | vauthors = Herzog A, Shedden-Mora MC, Jordan P, Löwe B | title = Duration of untreated illness in patients with somatoform disorders | journal = Journal of Psychosomatic Research | volume = 107 | pages = 1–6 | date = April 2018 | pmid = 29502757 | doi = 10.1016/j.jpsychores.2018.01.011 }} Currently, there is a lack of specialised treatment services for functional disorders in many countries.{{cite journal | vauthors = Kohlmann S, Löwe B, Shedden-Mora MC | title = Health Care for Persistent Somatic Symptoms Across Europe: A Qualitative Evaluation of the EURONET-SOMA Expert Discussion | journal = Frontiers in Psychiatry | volume = 9 | pages = 646 | date = 2018-12-07 | pmid = 30581394 | pmc = 6292948 | doi = 10.3389/fpsyt.2018.00646 | doi-access = free }} However, research is growing in this area, and it is hoped that the implementation of the increased scientific understanding of functional disorders and their treatment will allow effective clinical services supporting individuals with functional disorders to develop.{{cite journal | vauthors = Mars RA, Yang Y, Ward T, Houtti M, Priya S, Lekatz HR, Tang X, Sun Z, Kalari KR, Korem T, Bhattarai Y, Zheng T, Bar N, Frost G, Johnson AJ, van Treuren W, Han S, Ordog T, Grover M, Sonnenburg J, D'Amato M, Camilleri M, Elinav E, Segal E, Blekhman R, Farrugia G, Swann JR, Knights D, Kashyap PC | display-authors = 6 | title = Longitudinal Multi-omics Reveals Subset-Specific Mechanisms Underlying Irritable Bowel Syndrome | journal = Cell | volume = 183 | issue = 4 | pages = 1137–1140 | date = November 2020 | pmid = 33186523 | doi = 10.1016/j.cell.2020.10.040 | s2cid = 226308619 | doi-access = free }} Patient membership organisations/advocate groups have been instrumental in gaining recognition for individuals with these disorders.{{Cite web |title=HOME FND Hope |url=https://fndhope.org/ |access-date=2022-09-07 |website=FND Hope International |language=en-US}}{{Cite web |title=The IBS Network |url=https://www.theibsnetwork.org/ |access-date=2022-09-07 |website=www.theibsnetwork.org |language=en}}

Directions for research involve understanding more about the processes underlying functional disorders, identifying what leads to symptom persistence and improving integrated care/treatment pathways for patients.

Research into the biological mechanisms which underpin functional disorders is ongoing. Understanding how stress effects the body over a lifetime,{{Cite journal | vauthors = M Nater U, Fischer S, Ehlert U |date=2011-05-01 |title=Stress as a Pathophysiological Factor in Functional Somatic Syndromes |journal=Current Psychiatry Reviews |volume=7 |issue=2 |pages=152–169 |doi=10.2174/157340011796391184 }} for example via the immune{{cite journal | vauthors = Dantzer R, Heijnen CJ, Kavelaars A, Laye S, Capuron L | title = The neuroimmune basis of fatigue | journal = Trends in Neurosciences | volume = 37 | issue = 1 | pages = 39–46 | date = January 2014 | pmid = 24239063 | doi = 10.1016/j.tins.2013.10.003 | pmc = 3889707 }}{{cite journal | vauthors = Boeckxstaens GE, Wouters MM | title = Neuroimmune factors in functional gastrointestinal disorders: A focus on irritable bowel syndrome | journal = Neurogastroenterology and Motility | volume = 29 | issue = 6 | pages = e13007 | date = June 2017 | pmid = 28027594 | doi = 10.1111/nmo.13007 | s2cid = 44642749 | url = https://lirias.kuleuven.be/handle/123456789/568261 | url-access = subscription }} endocrine and autonomic nervous systems, is important Ying-Chih et.al 2020, Tak et. al. 2011, Nater et al. 2011). Subtle dysfunctions of these systems, for example through low grade chronic inflammation,{{cite journal | vauthors = Irwin MR | title = Inflammation at the intersection of behavior and somatic symptoms | journal = The Psychiatric Clinics of North America | volume = 34 | issue = 3 | pages = 605–620 | date = September 2011 | pmid = 21889682 | doi = 10.1016/j.psc.2011.05.005 | pmc = 3820277 }}{{cite journal | vauthors = Strawbridge R, Sartor ML, Scott F, Cleare AJ | title = Inflammatory proteins are altered in chronic fatigue syndrome-A systematic review and meta-analysis | journal = Neuroscience and Biobehavioral Reviews | volume = 107 | pages = 69–83 | date = December 2019 | pmid = 31465778 | doi = 10.1016/j.neubiorev.2019.08.011 | s2cid = 201645160 }} or dysfunctional breathing patterns,{{cite journal | vauthors = Gold AR | title = Functional somatic syndromes, anxiety disorders and the upper airway: a matter of paradigms | journal = Sleep Medicine Reviews | volume = 15 | issue = 6 | pages = 389–401 | date = December 2011 | pmid = 21295503 | doi = 10.1016/j.smrv.2010.11.004 }} are increasingly thought to underlie functional disorders and their treatment. However, more research is needed before these theoretical mechanisms can be used clinically to guide treatment for an individual patient.

• Idiopathic disease
• Functional gastrointestinal disorder
• Functional neurological symptom disorder
• Functional symptom
• Psychosomatic medicine

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Category:Diseases and disorders

Category:Medical terminology