Irritable bowel syndrome

The primary symptoms of IBS are abdominal pain or discomfort in association with frequent diarrhea or constipation and a change in bowel habits.{{cite journal | vauthors = Schmulson MW, Chang L | title = Diagnostic approach to the patient with irritable bowel syndrome | journal = The American Journal of Medicine | volume = 107 | issue = 5A | pages = 20S–26S | date = November 1999 | pmid = 10588169 | doi = 10.1016/S0002-9343(99)00278-8 }} Symptoms usually are experienced as acute attacks that subside within one day, but recurrent attacks are likely.{{Cite book|title=Fifth Edition: Diseases of the Human Body| vauthors =Tamparo C |publisher=F.A. Davis Company|year=2011|isbn=978-0-8036-2505-1|location=Philadelphia, PA|page=407}} There may also be urgency for bowel movements, a feeling of incomplete evacuation (tenesmus) or bloating. In some cases, the symptoms are relieved by bowel movements.

People with IBS, more commonly than others, have gastroesophageal reflux, symptoms relating to the genitourinary system, fibromyalgia, headache, backache, and psychiatric symptoms such as depression, sleep disorders,{{cite journal | vauthors = Wang B, Duan R, Duan L | title = Prevalence of sleep disorder in irritable bowel syndrome: A systematic review with meta-analysis | language = en-US | journal = Saudi Journal of Gastroenterology | volume = 24 | issue = 3 | pages = 141–150 | date = May–Jun 2018 | pmid = 29652034 | pmc = 5985632 | doi = 10.4103/sjg.SJG_603_17 | doi-access = free }} and anxiety.{{cite journal | vauthors = Talley NJ | title = Irritable bowel syndrome | journal = Internal Medicine Journal | volume = 36 | issue = 11 | pages = 724–728 | date = November 2006 | pmid = 17040359 | pmc = 1761148 | doi = 10.1111/j.1445-5994.2006.01217.x }} About a third of adults who have IBS also report sexual dysfunction, typically in the form of a reduction in libido.{{cite journal | vauthors = Sperber AD, Dekel R | title = Irritable Bowel Syndrome and Co-morbid Gastrointestinal and Extra-gastrointestinal Functional Syndromes | journal = Journal of Neurogastroenterology and Motility | volume = 16 | issue = 2 | pages = 113–119 | date = April 2010 | pmid = 20535341 | pmc = 2879857 | doi = 10.5056/jnm.2010.16.2.113 }}

While the causes of IBS are still unknown, it is believed that the entire gut–brain axis is affected.{{cite journal | vauthors = Ohman L, Simrén M | title = Pathogenesis of IBS: role of inflammation, immunity and neuroimmune interactions | journal = Nature Reviews. Gastroenterology & Hepatology | volume = 7 | issue = 3 | pages = 163–173 | date = March 2010 | pmid = 20101257 | doi = 10.1038/nrgastro.2010.4 | s2cid = 20898797 }}

Recent findings suggest that an allergy-triggered peripheral immune mechanism may underlie the symptoms associated with abdominal pain in patients with irritable bowel syndrome.{{cite journal | vauthors = Rothenberg ME | title = An Allergic Basis for Abdominal Pain | journal = The New England Journal of Medicine | volume = 384 | issue = 22 | pages = 2156–2158 | date = June 2021 | pmid = 34077648 | doi = 10.1056/NEJMcibr2104146 | s2cid = 235322218 }}

Studies showed that a considerable portion of patients with IBS experience immediate mucosal responses to certain foods. These responses, observed through fluorescein leakage and cell shedding during Confocal endoscopy, were linked to significant symptom relief in more than 70% of patients following customized dietary restrictions. This implies that localized immune reactions and compromised barrier function, beyond traditional IgE-mediated allergies, might play a role in IBS symptoms. Pavan F, Costantino A, Tontini GE, Elli L, Siragusa N, Lasagni G, Dubini M, Scricciolo A, Vecchi M. Is IBS a Food Allergy? Confocal Laser Endomicroscopy Findings in Patients with IBS: A Narrative Review. Applied Sciences. 2025; 15(7):3717. https://doi.org/10.3390/app15073717

People who are younger than 50, women, and those with a family history of the condition are more likely to develop IBS. Further risk factors are anxiety, depression, and stress.{{Cite journal |last=Creed |first=Francis |date=September 2019 |title=Review article: the incidence and risk factors for irritable bowel syndrome in population-based studies |url=https://onlinelibrary.wiley.com/doi/10.1111/apt.15396 |journal=Alimentary Pharmacology & Therapeutics |language=en |volume=50 |issue=5 |pages=507–516 |doi=10.1111/apt.15396 |pmid=31313850 |issn=0269-2813}} The risk of developing IBS increases six-fold after having a gastrointestinal infection (gastroenteritis).{{cite journal | vauthors = Enck P, Aziz Q, Barbara G, Farmer AD, Fukudo S, Mayer EA, Niesler B, Quigley EM, Rajilić-Stojanović M, Schemann M, Schwille-Kiuntke J, Simren M, Zipfel S, Spiller RC | title = Irritable bowel syndrome | journal = Nature Reviews. Disease Primers | volume = 2 | page = 16014 | date = March 2016 | pmid = 27159638 | pmc = 5001845 | doi = 10.1038/nrdp.2016.14 }} This is also called post-infectious IBS. The risk of developing IBS following an infection is further increased in those who also had a prolonged fever during the illness.{{cite journal |vauthors=Thabane M, Kottachchi DT, Marshall JK |date=August 2007 |title=Systematic review and meta-analysis: The incidence and prognosis of post-infectious irritable bowel syndrome |journal=Alimentary Pharmacology & Therapeutics |volume=26 |issue=4 |pages=535–544 |doi=10.1111/j.1365-2036.2007.03399.x |pmid=17661757 |s2cid=41136248 |doi-access=free}} Antibiotic use also appears to increase the risk of developing IBS.{{cite journal | vauthors = Shanahan F, Quigley EM | title = Manipulation of the microbiota for treatment of IBS and IBD-challenges and controversies | journal = Gastroenterology | volume = 146 | issue = 6 | pages = 1554–1563 | date = May 2014 | pmid = 24486051 | doi = 10.1053/j.gastro.2014.01.050 | doi-access = free }} Genetic defects in innate immunity and epithelial homeostasis increase the risk of developing both post-infectious as well as other forms of IBS.

The role of the brain–gut axis in IBS has been suggested since the 1990s and childhood physical and psychological abuse is often associated with the development of IBS. It is believed that psychological stress may trigger IBS in predisposed individuals.

Given the high levels of anxiety experienced by people with IBS and the overlap with conditions such as fibromyalgia and chronic fatigue syndrome, a potential explanation for IBS involves a disruption of the stress system. The stress response in the body involves the hypothalamic–pituitary–adrenal axis (HPA) and the sympathetic nervous system, both of which have been shown to operate abnormally in people with IBS. Psychiatric illness or anxiety precedes IBS symptoms in two-thirds of people with IBS, and psychological traits predispose previously healthy people to developing IBS after gastroenteritis.{{cite journal | vauthors = Spiller R, Aziz Q, Creed F, Emmanuel A, Houghton L, Hungin P, Jones R, Kumar D, Rubin G, Trudgill N, Whorwell P | title = Guidelines on the irritable bowel syndrome: mechanisms and practical management | journal = Gut | volume = 56 | issue = 12 | pages = 1770–1798 | date = December 2007 | pmid = 17488783 | pmc = 2095723 | doi = 10.1136/gut.2007.119446 }}{{cite journal | vauthors = Fukudo S | title = Role of corticotropin-releasing hormone in irritable bowel syndrome and intestinal inflammation | journal = Journal of Gastroenterology | volume = 42 | issue = Suppl 17 | pages = 48–51 | date = January 2007 | pmid = 17238026 | doi = 10.1007/s00535-006-1942-7 | s2cid = 26067985 }} Individuals with IBS also report high rates of sleep disturbances such as trouble falling asleep and frequent arousal throughout the night.{{cite journal | vauthors = Mróz M, Czub M, Brytek-Matera A | title = Heart Rate Variability-An Index of the Efficacy of Complementary Therapies in Irritable Bowel Syndrome: A Systematic Review | journal = Nutrients | volume = 14 | issue = 16 | pages = 3447 | date = August 2022 | pmid = 36014953 | pmc = 9416471 | doi = 10.3390/nu14163447 | doi-access = free }}

Approximately 10 percent of IBS cases are triggered by an acute gastroenteritis infection.{{cite web|title=Post-infectious IBS|url=https://aboutibs.org/what-is-ibs-sidenav/post-infectious-ibs.html|access-date=2021-04-02|website=aboutibs.org|date=March 8, 2021}} The CdtB toxin is produced by bacteria causing gastroenteritis and the host may develop an autoimmunity when host antibodies to CdtB cross-react with vinculin.{{cite journal | vauthors = Barbara G, Grover M, Bercik P, Corsetti M, Ghoshal UC, Ohman L, Rajilić-Stojanović M | title = Rome Foundation Working Team Report on Post-Infection Irritable Bowel Syndrome | language = en | journal = Gastroenterology | volume = 156 | issue = 1 | pages = 46–58.e7 | date = January 2019 | pmid = 30009817 | pmc = 6309514 | doi = 10.1053/j.gastro.2018.07.011 | url = https://www.gastrojournal.org/article/S0016-5085(18)34766-8/abstract }} Genetic defects relating to the innate immune system and epithelial barrier as well as high stress and anxiety levels appear to increase the risk of developing post-infectious IBS. Post-infectious IBS usually manifests itself as the diarrhea-predominant subtype. Evidence has demonstrated that the release of high levels of proinflammatory cytokines during acute enteric infection causes increased gut permeability leading to translocation of the commensal bacteria across the epithelial barrier; this in turn can result in significant damage to local tissues, which can develop into chronic gut abnormalities in sensitive individuals. However, increased gut permeability is strongly associated with IBS regardless of whether IBS was initiated by an infection or not.{{cite journal | vauthors = Beatty JK, Bhargava A, Buret AG | title = Post-infectious irritable bowel syndrome: mechanistic insights into chronic disturbances following enteric infection | journal = World Journal of Gastroenterology | volume = 20 | issue = 14 | pages = 3976–85 | date = April 2014 | pmid = 24744587 | pmc = 3983453 | doi = 10.3748/wjg.v20.i14.3976 | doi-access = free }} A link between small intestinal bacterial overgrowth and tropical sprue has been proposed to be involved as a cause of post-infectious IBS.{{cite journal | vauthors = Ghoshal UC, Gwee KA | s2cid = 33660302 | title = Post-infectious IBS, tropical sprue and small intestinal bacterial overgrowth: the missing link | journal = Nature Reviews. Gastroenterology & Hepatology | volume = 14 | issue = 7 | pages = 435–441 | date = July 2017 | pmid = 28513629 | doi = 10.1038/nrgastro.2017.37 }}

Small intestinal bacterial overgrowth (SIBO) occurs with greater frequency in people who have been diagnosed with IBS compared to healthy controls.{{cite journal | vauthors = Chen B, Kim JJ, Zhang Y, Du L, Dai N | title = Prevalence and predictors of small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and meta-analysis | journal = Journal of Gastroenterology | volume = 53 | issue = 7 | pages = 807–818 | date = July 2018 | pmid = 29761234 | doi = 10.1007/s00535-018-1476-9 | s2cid = 46889298 }} SIBO is most common in diarrhea-predominant IBS but also occurs in constipation-predominant IBS more frequently than healthy controls. Symptoms of SIBO include bloating, abdominal pain, diarrhea or constipation among others. IBS may be the result of the immune system interacting abnormally with gut microbiota resulting in an abnormal cytokine signalling profile.{{cite journal | vauthors = Ghoshal UC, Srivastava D | title = Irritable bowel syndrome and small intestinal bacterial overgrowth: meaningful association or unnecessary hype | journal = World Journal of Gastroenterology | volume = 20 | issue = 10 | pages = 2482–91 | date = March 2014 | pmid = 24627585 | pmc = 3949258 | doi = 10.3748/wjg.v20.i10.2482 | doi-access = free }}

Certain bacteria are found in lower or higher abundance when compared with healthy individuals. Generally Bacteroidota, Bacillota, and Pseudomonadota are increased and Actinomycetota, Bifidobacteria, and Lactobacillus are decreased. Within the human gut, there are common phyla found. The most common is Bacillota. This includes Lactobacillus, which is found to have a decrease in people with IBS, and Streptococcus, which is shown to have an increase in abundance. Within this phylum, species in the class Clostridia are shown to have an increase, specifically Ruminococcus and Dorea. The family Lachnospiraceae presents an increase in IBS-D patients. The second most common phylum is Bacteroidota. In people with IBS, the Bacteroidota phylum has been shown to have an overall decrease, but an increase in the genus Bacteroides. IBS-D shows a decrease for the phylum Actinomycetota and an increase in Pseudomonadota, specifically in the family Enterobacteriaceae.{{cite journal | vauthors = Bennet SM, Ohman L, Simren M | title = Gut microbiota as potential orchestrators of irritable bowel syndrome | journal = Gut and Liver | volume = 9 | issue = 3 | pages = 318–31 | date = May 2015 | pmid = 25918261 | pmc = 4413965 | doi = 10.5009/gnl14344 }}

Alterations of gut microbiota (dysbiosis) are associated with the intestinal manifestations of IBS, but also with the psychiatric morbidity that coexists in up to 80% of people with IBS.

File:Causes of irritable bowel syndrome (bar charts).png

Protozoal infections can cause symptoms that mirror specific IBS subtypes,{{cite journal | vauthors = Stark D, van Hal S, Marriott D, Ellis J, Harkness J | title = Irritable bowel syndrome: a review on the role of intestinal protozoa and the importance of their detection and diagnosis | journal = International Journal for Parasitology | volume = 37 | issue = 1 | pages = 11–20 | date = January 2007 | pmid = 17070814 | doi = 10.1016/j.ijpara.2006.09.009 }} e.g., infection by certain substypes of Blastocystis hominis (blastocystosis).{{cite journal | vauthors = Wawrzyniak I, Poirier P, Viscogliosi E, Dionigia M, Texier C, Delbac F, Alaoui HE | title = Blastocystis, an unrecognized parasite: an overview of pathogenesis and diagnosis | journal = Therapeutic Advances in Infectious Disease | volume = 1 | issue = 5 | pages = 167–78 | date = October 2013 | pmid = 25165551 | pmc = 4040727 | doi = 10.1177/2049936113504754 | quote = Recent in vitro and in vivo studies have shed new light on the pathogenic power of this parasite, suggesting that Blastocystis sp. infection is associated with a variety of gastrointestinal disorders, may play a significant role in irritable bowel syndrome, and may be linked with cutaneous lesions (urticaria). }}{{cite journal | vauthors = Roberts T, Stark D, Harkness J, Ellis J | title = Update on the pathogenic potential and treatment options for Blastocystis sp | journal = Gut Pathogens | volume = 6 | page = 17 | year = 2014 | pmid = 24883113 | pmc = 4039988 | doi = 10.1186/1757-4749-6-17 | doi-access = free }} Many people regard these organisms as incidental findings, and unrelated to symptoms of IBS.

Blastocystis and Dientamoeba fragilis colonisation occurs more commonly in IBS affected individuals but their role in the condition is unclear.{{Cite journal |last1=Olyaiee |first1=Alireza |last2=Sadeghi |first2=Amir |last3=Yadegar |first3=Abbas |last4=Mirsamadi |first4=Elnaz Sadat |last5=Mirjalali |first5=Hamed |date=2022-06-20 |title=Gut Microbiota Shifting in Irritable Bowel Syndrome: The Mysterious Role of Blastocystis sp. |journal=Frontiers in Medicine |volume=9 |doi=10.3389/fmed.2022.890127 |doi-access=free |issn=2296-858X |pmc=9251125 |pmid=35795640}}

Vitamin D deficiency is more common in individuals affected by IBS.{{cite journal | vauthors = Williams CE, Williams EA, Corfe BM | s2cid = 19291568 | title = Vitamin D status in irritable bowel syndrome and the impact of supplementation on symptoms: what do we know and what do we need to know? | journal = European Journal of Clinical Nutrition | volume = 72 | issue = 10 | pages = 1358–1363 | date = October 2018 | pmid = 29367731 | doi = 10.1038/s41430-017-0064-z | url = http://eprints.whiterose.ac.uk/127402/3/Williams%20et%20al%20EJCN%20Body%20Text%20R2%20Clean.pdf }}{{cite journal | vauthors = Ferguson LR, Laing B, Marlow G, Bishop K | title = The role of vitamin D in reducing gastrointestinal disease risk and assessment of individual dietary intake needs: Focus on genetic and genomic technologies | journal = Molecular Nutrition & Food Research | volume = 60 | issue = 1 | pages = 119–33 | date = January 2016 | pmid = 26251177 | doi = 10.1002/mnfr.201500243 }} Vitamin D is involved in regulating triggers for IBS including the gut microbiome, inflammatory processes and immune responses, as well as psychosocial factors.{{cite journal |vauthors=Barbalho SM, Goulart RA, Araújo AC, Guiguer ÉL, Bechara MD |s2cid=73484679 |title=Irritable bowel syndrome: a review of the general aspects and the potential role of vitamin D |journal=Expert Rev Gastroenterol Hepatol |volume=13 |issue=4 |pages=345–359 |date=April 2019 |pmid=30791775 |doi=10.1080/17474124.2019.1570137 }}

SCN5A mutations are found in a small number of people who have IBS, particularly the constipation-predominant variant (IBS-C).{{cite journal | vauthors = Beyder A, Farrugia G | title = Ion channelopathies in functional GI disorders | journal = American Journal of Physiology. Gastrointestinal and Liver Physiology | volume = 311 | issue = 4 | pages = G581–G586 | year = 2016 | pmid = 27514480 | doi = 10.1152/ajpgi.00237.2016 | pmc=5142191}}{{cite journal | vauthors = Verstraelen TE, Ter Bekke RM, Volders PG, Masclee AA, Kruimel JW | title = The role of the SCN5A-encoded channelopathy in irritable bowel syndrome and other gastrointestinal disorders | journal = Neurogastroenterology & Motility | volume = 27 | issue = 7 | pages = 906–13 | year = 2015 | pmid = 25898860 | doi = 10.1111/nmo.12569 | s2cid = 5055360 }} The resulting defect leads to disruption in bowel function, by affecting the Nav1.5 channel, in smooth muscle of the colon and pacemaker cells.{{Cite journal |last1=Ou |first1=Y. |last2=Gibbons |first2=S. J. |last3=Miller |first3=S. M. |last4=Strege |first4=P. R. |last5=Rich |first5=A. |last6=Distad |first6=M. A. |last7=Ackerman |first7=M. J. |last8=Rae |first8=J. L. |last9=Szurszewski |first9=J. H. |last10=Farrugia |first10=G. |date=October 2002 |title=SCN5A is expressed in human jejunal circular smooth muscle cells |url=https://pubmed.ncbi.nlm.nih.gov/12358675/ |journal=Neurogastroenterology and Motility |volume=14 |issue=5 |pages=477–486 |doi=10.1046/j.1365-2982.2002.00348.x |issn=1350-1925 |pmid=12358675}}{{Cite journal |last1=Strege |first1=Peter R. |last2=Ou |first2=Yijun |last3=Sha |first3=Lei |last4=Rich |first4=Adam |last5=Gibbons |first5=Simon J. |last6=Szurszewski |first6=Joseph H. |last7=Sarr |first7=Michael G. |last8=Farrugia |first8=Gianrico |date=December 2003 |title=Sodium current in human intestinal interstitial cells of Cajal |url=https://pubmed.ncbi.nlm.nih.gov/12893628/ |journal=American Journal of Physiology. Gastrointestinal and Liver Physiology |volume=285 |issue=6 |pages=G1111–1121 |doi=10.1152/ajpgi.00152.2003 |issn=0193-1857 |pmid=12893628}}{{Cite journal |last1=Der-Silaphet |first1=T. |last2=Malysz |first2=J. |last3=Hagel |first3=S. |last4=Larry Arsenault |first4=A. |last5=Huizinga |first5=J. D. |date=April 1998 |title=Interstitial cells of cajal direct normal propulsive contractile activity in the mouse small intestine |url=https://pubmed.ncbi.nlm.nih.gov/9516393/ |journal=Gastroenterology |volume=114 |issue=4 |pages=724–736 |doi=10.1016/s0016-5085(98)70586-4 |issn=0016-5085 |pmid=9516393}}

A lack of physical activity is associated with an increased prevalence of IBS. Liu, Liang, et al. "A cross-sectional study of irritable bowel syndrome in nurses in China: prevalence and associated psychological and lifestyle factors." Journal of Zhejiang University-SCIENCE B 15 (2014): 590-597.

IBS is more prevalent in obese patients.{{cite journal | vauthors = Kim JH, Yi DY, Lee YM, Choi YJ, Kim JY, Hong YH, Park JY, Kim SY, Lee NM, Yun SW, Chae SA, Lim IS, Choi ES, Jeong IS | title = Association between body mass index and fecal calprotectin levels in children and adolescents with irritable bowel syndrome | journal = Medicine | volume = 101 | issue = 32 | pages = e29968 | date = August 2022 | pmid = 35960084 | doi = 10.1097/MD.0000000000029968 | pmc = 9371505 }}

Genetic, environmental, and psychological factors seem to be important in the development of IBS. The condition also has a genetic component even though there is a predominant influence of environmental factors.{{cite journal | vauthors = Talley NJ | title = Genes and environment in irritable bowel syndrome: one step forward | journal = Gut | volume = 55 | issue = 12 | pages = 1694–6 | date = December 2006 | pmid = 17124153 | pmc = 1856457 | doi = 10.1136/gut.2006.108837 }}

Dysregulated brain-gut axis, abnormal serotonin/5-hydroxytryptamine (5-HT) metabolism, and high density of mucosal nerve fibers in the intestines have been implicated in the mechanisms of IBS. A number of 5-HT receptor subtypes were involved in the IBS symptoms, including 5-HT₃, 5-HT₄, and 5-HT₇ receptors. High levels of 5-HT₇ receptor-expressing mucosal nerve fibers were observed in the colon of IBS patients. A role of 5-HT7 receptor in intestinal hyperalgesia was demonstrated in mouse models with visceral hypersensitivity, of which a novel 5-HT₇ receptor antagonist administered by mouth reduced intestinal pain levels.{{cite journal | vauthors = Chang WY, Yang YT, She MP, Tu CH, Lee TC, Wu MS, Sun CH, Hsin LW, Yu LC | title = 5-HT 7 receptor-dependent intestinal neurite outgrowth contributes to visceral hypersensitivity in irritable bowel syndrome | journal = Laboratory Investigation | pmid = 35585132 | doi = 10.1038/s41374-022-00800-z| year = 2022 | volume = 102 | issue = 9 | pages = 1023–1037 | pmc = 9420680 | s2cid = 248867188 }}

Abnormalities occur in the gut flora of individuals who have IBS, such as reduced diversity, a decrease in bacteria belonging to the phylum Bacteroidota, and an increase in those belonging to the phylum Bacillota.{{cite journal | vauthors = Collins SM | s2cid = 10676400 | title = A role for the gut microbiota in IBS | journal = Nature Reviews. Gastroenterology & Hepatology | volume = 11 | issue = 8 | pages = 497–505 | date = August 2014 | pmid = 24751910 | doi = 10.1038/nrgastro.2014.40 }} The changes in gut flora are most profound in individuals who have diarrhoea-predominant IBS. Antibodies against common components (namely flagellin) of the commensal gut flora are a common occurrence in IBS affected individuals.{{cite journal | vauthors = Cremon C, Carini G, De Giorgio R, Stanghellini V, Corinaldesi R, Barbara G | s2cid = 207219334 | title = Intestinal dysbiosis in irritable bowel syndrome: etiological factor or epiphenomenon? | journal = Expert Review of Molecular Diagnostics | volume = 10 | issue = 4 | pages = 389–93 | date = May 2010 | pmid = 20465494 | doi = 10.1586/erm.10.33 }}

Chronic low-grade inflammation commonly occurs in IBS affected individuals with abnormalities found including increased enterochromaffin cells, intraepithelial lymphocytes, and mast cells resulting in chronic immune-mediated inflammation of the gut mucosa.{{cite journal | vauthors = Wouters MM, Vicario M, Santos J | s2cid = 3456082 | title = The role of mast cells in functional GI disorders | journal = Gut | volume = 65 | issue = 1 | pages = 155–68 | date = January 2016 | pmid = 26194403 | doi = 10.1136/gutjnl-2015-309151 | doi-access = free }}{{cite journal | vauthors = Schmulson M, Bielsa MV, Carmona-Sánchez R, Hernández A, López-Colombo A, López Vidal Y, Peláez-Luna M, Remes-Troche JM, Tamayo JL, Valdovinos MA | title = Microbiota, gastrointestinal infections, low-grade inflammation, and antibiotic therapy in irritable bowel syndrome: an evidence-based review | language = es | journal = Revista de Gastroenterologia de Mexico | volume = 79 | issue = 2 | pages = 96–134 | year = 2014 | pmid = 24857420 | doi = 10.1016/j.rgmx.2014.01.004 | doi-access = free }} IBS has been reported in greater quantities in multigenerational families with IBS than in the regular population.{{cite journal | vauthors = Saito YA | title = The role of genetics in IBS | journal = Gastroenterology Clinics of North America | volume = 40 | issue = 1 | pages = 45–67 | date = March 2011 | pmid = 21333900 | pmc = 3056499 | doi = 10.1016/j.gtc.2010.12.011 }} It is believed that psychological stress can induce increased inflammation and thereby cause IBS to develop in predisposed individuals.

No specific laboratory or imaging tests can diagnose irritable bowel syndrome. Diagnosis should be based on symptoms, the exclusion of worrisome features, and the performance of specific investigations to rule out organic diseases that may present similar symptoms.{{cite journal | vauthors = Yawn BP, Lydick E, Locke GR, Wollan PC, Bertram SL, Kurland MJ | title = Do published guidelines for evaluation of irritable bowel syndrome reflect practice? | journal = BMC Gastroenterology | volume = 1 | page = 11 | year = 2001 | pmid = 11701092 | pmc = 59674 | doi = 10.1186/1471-230X-1-11 | doi-access = free }}

The recommendations for physicians are to minimize the use of medical investigations.{{cite journal | vauthors = Irvine AJ, Chey WD, Ford AC | s2cid = 269053 | title = Screening for Celiac Disease in Irritable Bowel Syndrome: An Updated Systematic Review and Meta-analysis | journal = The American Journal of Gastroenterology | volume = 112 | issue = 1 | pages = 65–76 | date = January 2017 | pmid = 27753436 | doi = 10.1038/ajg.2016.466 | type = Review | quote = Although IBS is not a diagnosis of exclusion, with physicians advised to minimize the use of investigations, the gastrointestinal (GI) tract has a limited repertoire of symptoms, meaning that abdominal pain and a change in bowel habit is not specific to the disorder. | url = http://eprints.whiterose.ac.uk/106483/3/AJG-16-1318R1%20CLEAN.pdf }} The Rome criteria are typically used for diagnosis. They allow the diagnosis to be based only on symptoms, but no criteria based solely on symptoms is sufficiently accurate to diagnose IBS.{{cite journal | vauthors = Drossman DA | s2cid = 6441439 | title = Functional Gastrointestinal Disorders: History, Pathophysiology, Clinical Features and Rome IV | journal = Gastroenterology | volume = 150 | issue = 6 | pages = 1262–1279.e2 | date = February 2016 | pmid = 27144617 | doi = 10.1053/j.gastro.2016.02.032 | url = https://cdr.lib.unc.edu/downloads/12579z328 }}{{cite journal | vauthors = Saha L | title = Irritable bowel syndrome: pathogenesis, diagnosis, treatment, and evidence-based medicine | journal = World Journal of Gastroenterology | volume = 20 | issue = 22 | pages = 6759–73 | date = June 2014 | pmid = 24944467 | pmc = 4051916 | doi = 10.3748/wjg.v20.i22.6759 | type = Review | doi-access = free }} Worrisome features include onset at greater than 50 years of age, weight loss, blood in the stool, iron-deficiency anemia, or a family history of colon cancer, celiac disease, or inflammatory bowel disease. The criteria for selecting tests and investigations also depends on the level of available medical resources.{{cite web |date=Sep 2015 |title=World Gastroenterology Organisation Global Guidelines. Irritable Bowel Syndrome: a Global Perspective |url=http://www.worldgastroenterology.org/UserFiles/file/guidelines/irritable-bowel-syndrome-english-2015.pdf |url-status=live |archive-url=https://web.archive.org/web/20160527194952/http://www.worldgastroenterology.org/UserFiles/file/guidelines/irritable-bowel-syndrome-english-2015.pdf |archive-date=May 27, 2016 |access-date=24 Apr 2016 |publisher=World Gastroenterology Organisation |df=mdy-all}}

The Rome IV criteria for diagnosing IBS include recurrent abdominal pain, on average, at least one day/week in the last three months, associated with additional stool- or defecation-related criteria.{{cite web |title=Rome IV Criteria |url=https://theromefoundation.org/rome-iv/rome-iv-criteria/ |access-date=2022-04-14 |website=Rome Foundation |language=en-US}} The algorithm may include additional tests to guard against misdiagnosis of other diseases as IBS. Such "red flag" symptoms that may indicate other diseases as well include weight loss, gastrointestinal bleeding, anemia, or nocturnal symptoms. However, red flag conditions may not always contribute to accuracy in diagnosis; for instance, as many as 31% of people with IBS have blood in their stool, many possibly from hemorrhoidal bleeding.{{cite journal | vauthors = Fass R, Longstreth GF, Pimentel M, Fullerton S, Russak SM, Chiou CF, Reyes E, Crane P, Eisen G, McCarberg B, Ofman J | title = Evidence- and consensus-based practice guidelines for the diagnosis of irritable bowel syndrome | journal = Archives of Internal Medicine | volume = 161 | issue = 17 | pages = 2081–8 | date = September 2001 | pmid = 11570936 | doi = 10.1001/archinte.161.17.2081 | doi-access = free }}

Investigations are performed to exclude other conditions:{{citation needed|date=June 2021}}

• Stool microscopy and culture (to exclude infectious conditions)
• Blood tests: full blood examination, liver function tests, erythrocyte sedimentation rate, and serological testing for coeliac disease
• Abdominal ultrasound (to exclude gallstones and other biliary tract diseases)
• Endoscopy and biopsies (to exclude peptic ulcer disease, coeliac disease, inflammatory bowel disease, and malignancies)
• Hydrogen breath testing (to exclude fructose and lactose malabsorption)

Colon cancer, inflammatory bowel disease, thyroid disorders (hyperthyroidism or hypothyroidism), and giardiasis can all feature abnormal defecation and abdominal pain. Less common causes of this symptom profile are carcinoid syndrome, microscopic colitis, bacterial overgrowth, and eosinophilic gastroenteritis; IBS is, however, a common presentation, and testing for these conditions would yield low numbers of positive results, so it is considered difficult to justify the expense.{{cite book| vauthors = Hauser C |title=Mayo Clinic Gastroenterology and Hepatology Board Review|url=https://books.google.com/books?id=nStxzRQlNaAC&pg=PA225|access-date=October 24, 2010|year= 2005|publisher=CRC Press|isbn=978-0-203-50274-7|page=225–|url-status=live|archive-url=https://web.archive.org/web/20130510090901/http://books.google.com/books?id=nStxzRQlNaAC&pg=PA225|archive-date=May 10, 2013|df=mdy-all}} Conditions that may present similarly include celiac disease, bile acid malabsorption, colon cancer, and dyssynergic defecation.

Ruling out parasitic infections, lactose intolerance, small intestinal bacterial overgrowth, and celiac disease is recommended before a diagnosis of IBS is made. An upper endoscopy with small bowel biopsies is necessary to identify the presence of celiac disease.{{cite journal | vauthors = El-Salhy M | title = Irritable bowel syndrome: diagnosis and pathogenesis | journal = World Journal of Gastroenterology | volume = 18 | issue = 37 | pages = 5151–63 | date = October 2012 | pmid = 23066308 | pmc = 3468846 | doi = 10.3748/wjg.v18.i37.5151 | doi-access = free }} An ileocolonoscopy with biopsies is useful to exclude Crohn's disease and ulcerative colitis (Inflammatory bowel disease).

Some people, managed for years for IBS, may have non-celiac gluten sensitivity (NCGS).{{cite journal | vauthors = Levy J, Bernstein L, Silber N | title = Celiac disease: an immune dysregulation syndrome | journal = Current Problems in Pediatric and Adolescent Health Care | volume = 44 | issue = 11 | pages = 324–7 | date = December 2014 | pmid = 25499458 | doi = 10.1016/j.cppeds.2014.10.002 }} Gastrointestinal symptoms of IBS are clinically indistinguishable from those of NCGS, but the presence of any of the following non-intestinal manifestations suggest a possible NCGS: headache or migraine, "foggy mind", chronic fatigue, fibromyalgia,{{cite journal | vauthors = Volta U, Caio G, De Giorgio R, Henriksen C, Skodje G, Lundin KE | 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 = 477–91 | date = June 2015 | pmid = 26060112 | doi = 10.1016/j.bpg.2015.04.006 }}{{cite journal | vauthors = Rossi A, Di Lollo AC, Guzzo MP, Giacomelli C, Atzeni F, Bazzichi L, Di Franco M | title = Fibromyalgia and nutrition: what news? | journal = Clinical and Experimental Rheumatology | volume = 33 | issue = 1 Suppl 88 | pages = S117-25 | date = 2015 | pmid = 25786053 }}{{cite journal | vauthors = San Mauro Martín I, Garicano Vilar E, Collado Yurrutia L, Ciudad Cabañas MJ | title = [Is gluten the great etiopathogenic agent of disease in the XXI century?] | journal = Nutricion Hospitalaria | volume = 30 | issue = 6 | pages = 1203–10 | date = December 2014 | pmid = 25433099 | doi = 10.3305/nh.2014.30.6.7866 | df = mdy-all }} joint and muscle pain,{{cite journal | vauthors = Catassi C, Bai JC, Bonaz B, Bouma G, Calabrò A, Carroccio A, Castillejo G, Ciacci C, Cristofori F, Dolinsek J, Francavilla R, Elli L, Green P, Holtmeier W, Koehler P, Koletzko S, Meinhold C, Sanders D, Schumann M, Schuppan D, Ullrich R, Vécsei A, Volta U, Zevallos V, Sapone A, Fasano A | title = Non-Celiac Gluten sensitivity: the new frontier of gluten related disorders | journal = Nutrients | volume = 5 | issue = 10 | pages = 3839–53 | date = September 2013 | pmid = 24077239 | pmc = 3820047 | doi = 10.3390/nu5103839 | type = Review | doi-access = free }} leg or arm numbness, tingling of the extremities, dermatitis (eczema or skin rash), atopic disorders, allergy to one or more inhalants, foods or metals (such as mites, graminaceae, parietaria, cat or dog hair/dander, shellfish, or nickel), depression, anxiety, anemia, iron-deficiency anemia, folate deficiency, asthma, rhinitis, eating disorders, neuropsychiatric disorders (such as schizophrenia,{{cite journal | vauthors = Lebwohl B, Ludvigsson JF, Green PH | title = Celiac disease and non-celiac gluten sensitivity | journal = BMJ | volume = 351 | pages = h4347 | date = October 2015 | pmid = 26438584 | pmc = 4596973 | doi = 10.1136/bmj.h4347 | type = Review }} autism, peripheral neuropathy, ataxia, attention deficit hyperactivity disorder) or autoimmune diseases. An improvement with a gluten-free diet of immune-mediated symptoms, including autoimmune diseases, once having reasonably ruled out celiac disease and wheat allergy, is another way to realize a differential diagnosis.{{cite journal | vauthors = Fasano A, Sapone A, Zevallos V, Schuppan D | title = Nonceliac gluten sensitivity | journal = Gastroenterology | volume = 148 | issue = 6 | pages = 1195–204 | date = May 2015 | pmid = 25583468 | doi = 10.1053/j.gastro.2014.12.049 | type = Review | doi-access = free }}

People with IBS are at increased risk of being given inappropriate surgeries such as appendectomy, cholecystectomy, and hysterectomy due to being misdiagnosed as other medical conditions.{{cite journal | vauthors = Bixquert Jiménez M | title = Treatment of irritable bowel syndrome with probiotics. An etiopathogenic approach at last? | journal = Revista Española de Enfermedades Digestivas| volume = 101 | issue = 8 | pages = 553–64 | date = August 2009 | pmid = 19785495 | doi = 10.4321/s1130-01082009000800006 | df = mdy-all | doi-access = free }} Some common examples of misdiagnosis include infectious diseases, coeliac disease,{{cite journal | vauthors = Spiegel BM, DeRosa VP, Gralnek IM, Wang V, Dulai GS | title = Testing for celiac sprue in irritable bowel syndrome with predominant diarrhea: a cost-effectiveness analysis | journal = Gastroenterology | volume = 126 | issue = 7 | pages = 1721–32 | date = June 2004 | pmid = 15188167 | doi = 10.1053/j.gastro.2004.03.012 | url = https://zenodo.org/record/1235988 | doi-access = free }} Helicobacter pylori,{{cite journal | vauthors = Su YC, Wang WM, Wang SY, Lu SN, Chen LT, Wu DC, Chen CY, Jan CM, Horowitz M | title = The association between Helicobacter pylori infection and functional dyspepsia in patients with irritable bowel syndrome | journal = The American Journal of Gastroenterology | volume = 95 | issue = 8 | pages = 1900–5 | date = August 2000 | doi = 10.1111/j.1572-0241.2000.02252.x | pmid = 10950033 | s2cid = 22496041 }}{{cite journal | vauthors = Gerards C, Leodolter A, Glasbrenner B, Malfertheiner P | s2cid = 6877270 | title = H. pylori infection and visceral hypersensitivity in patients with irritable bowel syndrome | journal = Digestive Diseases | volume = 19 | issue = 2 | pages = 170–3 | year = 2001 | pmid = 11549828 | doi = 10.1159/000050673 }} parasites (non-protozoal).{{cite journal | vauthors = Grazioli B, Matera G, Laratta C, Schipani G, Guarnieri G, Spiniello E, Imeneo M, Amorosi A, Focà A, Luzza F | title = Giardia lamblia infection in patients with irritable bowel syndrome and dyspepsia: a prospective study | journal = World Journal of Gastroenterology | volume = 12 | issue = 12 | pages = 1941–4 | date = March 2006 | pmid = 16610003 | pmc = 4087522 | doi = 10.3748/wjg.v12.i12.1941 | df = mdy-all | doi-access = free }}{{cite journal | vauthors = Vernia P, Ricciardi MR, Frandina C, Bilotta T, Frieri G | title = Lactose malabsorption and irritable bowel syndrome. Effect of a long-term lactose-free diet | journal = The Italian Journal of Gastroenterology | volume = 27 | issue = 3 | pages = 117–21 | date = April 1995 | pmid = 7548919 }} The American College of Gastroenterology recommends all people with symptoms of IBS be tested for coeliac disease.

{{cite journal | vauthors = Brandt LJ, Chey WD, Foxx-Orenstein AE, Schiller LR, Schoenfeld PS, Spiegel BM, Talley NJ, Quigley EM | s2cid = 12556370 | title = An evidence-based position statement on the management of irritable bowel syndrome | journal = The American Journal of Gastroenterology | volume = 104 | issue = Suppl 1 | pages = S1-35 | date = January 2009 | pmid = 19521341 | doi = 10.1038/ajg.2008.122 | url = http://www.nature.com/ajg/journal/v104/n1s/pdf/ajg2008122a.pdf | archive-url = https://web.archive.org/web/20101205005043/http://www.nature.com/ajg/journal/v104/n1s/pdf/ajg2008122a.pdf | df = mdy-all | url-status = live | archive-date = December 5, 2010 }}

Bile acid malabsorption is also sometimes missed in people with diarrhea-predominant IBS. SeHCAT tests suggest around 30% of people with D-IBS have this condition, and most respond to bile acid sequestrants.{{cite journal | vauthors = Wedlake L, A'Hern R, Russell D, Thomas K, Walters JR, Andreyev HJ | title = Systematic review: the prevalence of idiopathic bile acid malabsorption as diagnosed by SeHCAT scanning in patients with diarrhoea-predominant irritable bowel syndrome | journal = Alimentary Pharmacology & Therapeutics | volume = 30 | issue = 7 | pages = 707–17 | date = October 2009 | pmid = 19570102 | doi = 10.1111/j.1365-2036.2009.04081.x | s2cid = 11327665 | doi-access = free }}

Several medical conditions, or comorbidities, appear with greater frequency in people with IBS.

• Neurological/psychiatric: A study of 97,593 individuals with IBS identified comorbidities such as headache, fibromyalgia, and depression.{{cite journal | vauthors = Cole JA, Rothman KJ, Cabral HJ, Zhang Y, Farraye FA | title = Migraine, fibromyalgia, and depression among people with IBS: a prevalence study | journal = BMC Gastroenterology | volume = 6 | page = 26 | date = September 2006 | pmid = 17007634 | pmc = 1592499 | doi = 10.1186/1471-230X-6-26 | doi-access = free }} IBS occurs in 51% of people with chronic fatigue syndrome and 49% of people with fibromyalgia, and psychiatric disorders occur in 94% of people with IBS.
• Channelopathy and muscular dystrophy: IBS and functional GI diseases are comorbidities of genetic channelopathies that cause cardiac conduction defects and neuromuscular dysfunction, and result also in alterations in GI motility, secretion, and sensation.{{cite journal | vauthors = Beyder A, Farrugia G | title = Ion channelopathies in functional GI disorders | journal = Am J Physiol Gastrointest Liver Physiol | volume = 311 | issue = 4 | pages = G581–G586 | date = October 2016 | pmid = 27514480 | doi = 10.1152/ajpgi.00237.2016| pmc = 5142191 | doi-access = free }} Similarly, IBS and FBD are highly prevalent in myotonic muscle dystrophies. Digestive symptoms may be the first sign of dystrophic disease and may precede the musculo-skeletal features by up to 10 years.{{cite journal | vauthors = Bellini M, Biagi S, Stasi C, Costa F, Mumolo MG, Ricchiuti A, Marchi S| title = Gastrointestinal manifestations in myotonic muscular dystrophy | journal = World J Gastroenterol | volume = 12 | issue = 12 | pages = 1821–1828 | date = March 2006 | pmid = 16609987 | doi = 10.3748/wjg.v12.i12.1821| pmc = 4087506 | doi-access = free }}
• Inflammatory bowel disease: IBS may be marginally associated with inflammatory bowel disease.{{cite journal | vauthors = Bercik P, Verdu EF, Collins SM | title = Is irritable bowel syndrome a low-grade inflammatory bowel disease? | journal = Gastroenterology Clinics of North America | volume = 34 | issue = 2 | pages = 235–45, vi–vii | date = June 2005 | pmid = 15862932 | doi = 10.1016/j.gtc.2005.02.007 }} Researchers have found some correlation between IBS and IBD,{{cite journal | vauthors = Quigley EM | title = Irritable bowel syndrome and inflammatory bowel disease: interrelated diseases? | journal = Chinese Journal of Digestive Diseases | volume = 6 | issue = 3 | pages = 122–32 | year = 2005 | pmid = 16045602 | doi = 10.1111/j.1443-9573.2005.00202.x }} noting that people with IBD experience IBS-like symptoms when their IBD is in remission.{{cite journal | vauthors = Simrén M, Axelsson J, Gillberg R, Abrahamsson H, Svedlund J, Björnsson ES | title = Quality of life in inflammatory bowel disease in remission: the impact of IBS-like symptoms and associated psychological factors | journal = The American Journal of Gastroenterology | volume = 97 | issue = 2 | pages = 389–96 | date = February 2002 | doi = 10.1016/S0002-9270(01)04037-0 | pmid = 11866278 }}{{cite journal | vauthors = Minderhoud IM, Oldenburg B, Wismeijer JA, van Berge Henegouwen GP, Smout AJ | s2cid = 7853070 | title = IBS-like symptoms in patients with inflammatory bowel disease in remission; relationships with quality of life and coping behavior | journal = Digestive Diseases and Sciences | volume = 49 | issue = 3 | pages = 469–74 | date = March 2004 | pmid = 15139501 | doi = 10.1023/B:DDAS.0000020506.84248.f9 }} A three-year study found that patients diagnosed with IBS were 16.3 times more likely to be diagnosed with IBD during the study period, although this is likely due to an initial misdiagnosis.{{cite journal | vauthors = García Rodríguez LA, Ruigómez A, Wallander MA, Johansson S, Olbe L | title = Detection of colorectal tumor and inflammatory bowel disease during follow-up of patients with initial diagnosis of irritable bowel syndrome | journal = Scandinavian Journal of Gastroenterology | volume = 35 | issue = 3 | pages = 306–11 | date = March 2000 | pmid = 10766326 | doi = 10.1080/003655200750024191 | s2cid = 218911104 }}{{Primary source inline|date=April 2024}}
• Abdominal surgery: People with IBS were at increased risk of having unnecessary gall bladder removal surgery not due to an increased risk of gallstones, but rather to abdominal pain, awareness of having gallstones, and inappropriate surgical indications.{{cite journal | vauthors = Corazziari E, Attili AF, Angeletti C, De Santis A | title = Gallstones, cholecystectomy and irritable bowel syndrome (IBS) MICOL population-based study | journal = Digestive and Liver Disease | volume = 40 | issue = 12 | pages = 944–50 | date = December 2008 | pmid = 18406218 | doi = 10.1016/j.dld.2008.02.013 }} These people also are 87% more likely to undergo abdominal and pelvic surgery and three times more likely to undergo gallbladder surgery.{{cite journal | vauthors = Cole JA, Yeaw JM, Cutone JA, Kuo B, Huang Z, Earnest DL, Walker AM | s2cid = 687380 | title = The incidence of abdominal and pelvic surgery among patients with irritable bowel syndrome | journal = Digestive Diseases and Sciences | volume = 50 | issue = 12 | pages = 2268–75 | date = December 2005 | pmid = 16416174 | doi = 10.1007/s10620-005-3047-1 }} Also, people with IBS were twice as likely to undergo hysterectomy.{{cite journal | vauthors = Longstreth GF, Yao JF | title = Irritable bowel syndrome and surgery: a multivariable analysis | journal = Gastroenterology | volume = 126 | issue = 7 | pages = 1665–73 | date = June 2004 | pmid = 15188159 | doi = 10.1053/j.gastro.2004.02.020 | doi-access = free }}
• Endometriosis: One study reported a statistically significant link between migraine headaches, IBS, and endometriosis.{{cite journal | vauthors = Tietjen GE, Bushnell CD, Herial NA, Utley C, White L, Hafeez F | title = Endometriosis is associated with prevalence of comorbid conditions in migraine | journal = Headache | volume = 47 | issue = 7 | pages = 1069–78 | year = 2007 | pmid = 17635599 | doi = 10.1111/j.1526-4610.2007.00784.x | s2cid = 34972425 | doi-access = free }}
• Other chronic disorders: Interstitial cystitis may be associated with other chronic pain syndromes, such as irritable bowel syndrome and fibromyalgia. The connection between these syndromes is unknown.{{cite web |url=http://www.mayoclinic.com/health/interstitial-cystitis/DS00497/DSECTION=4 |title=Interstitial cystitis: Risk factors |work=Mayo Clinic |date=January 20, 2009 |url-status=live |archive-url=https://web.archive.org/web/20080516123144/http://www.mayoclinic.com/health/interstitial-cystitis/DS00497/DSECTION%3D4 |archive-date=May 16, 2008 |df=mdy-all }}

IBS can be classified as diarrhea-predominant (IBS-D), constipation-predominant (IBS-C), with mixed/alternating stool pattern (IBS-M/IBS-A) or pain-predominant.{{cite journal |vauthors=Holten KB, Wetherington A, Bankston L |date=May 2003 |title=Diagnosing the patient with abdominal pain and altered bowel habits: is it irritable bowel syndrome? |url=http://www.aafp.org/afp/20030515/2157.html |url-status=live |journal=American Family Physician |volume=67 |issue=10 |pages=2157–2162 |pmid=12776965 |archive-url=https://web.archive.org/web/20080515204942/http://www.aafp.org/afp/20030515/2157.html |archive-date=May 15, 2008 |df=mdy-all}} In some individuals, IBS may have an acute onset and develop after an infectious illness characterized by two or more of: fever, vomiting, diarrhea, or positive stool culture. This post-infective syndrome has consequently been termed "post-infectious IBS" (IBS-PI).{{cite journal |vauthors=DuPont AW |date=February 2008 |title=Postinfectious irritable bowel syndrome |journal=Clinical Infectious Diseases |publisher=Oxford University Press |volume=46 |issue=4 |pages=594–599 |doi=10.1086/526774 |pmid=18205536 |doi-access=free}}{{cite journal |vauthors=Spiller R, Lam C |date=July 2012 |title=An Update on Post-infectious Irritable Bowel Syndrome: Role of Genetics, Immune Activation, Serotonin and Altered Microbiome |journal=Journal of Neurogastroenterology and Motility |volume=18 |issue=3 |pages=258–268 |doi=10.5056/jnm.2012.18.3.258 |pmc=3400813 |pmid=22837873}}{{cite journal |vauthors=Spiller RC |date=May 2003 |title=Postinfectious irritable bowel syndrome |journal=Gastroenterology |language=English |volume=124 |issue=6 |pages=1662–1671 |doi=10.1016/S0016-5085(03)00324-X |pmid=12761724}}{{cite journal |vauthors=Iacob T, Ţăţulescu DF, Dumitraşcu DL |date=2017 |title=Therapy of the postinfectious irritable bowel syndrome: an update |journal=Clujul Medical |volume=90 |issue=2 |pages=133–138 |doi=10.15386/cjmed-752 |pmc=5433563 |pmid=28559695}}

A number of treatments have been found to be effective, including fiber, talk therapy, antispasmodic and antidepressant medication, and peppermint oil.{{cite journal | vauthors = Ford AC, Talley NJ, Spiegel BM, Foxx-Orenstein AE, Schiller L, Quigley EM, Moayyedi P | title = Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis | journal = BMJ | volume = 337 | pages = a2313 | date = November 2008 | pmid = 19008265 | pmc = 2583392 | doi = 10.1136/bmj.a2313 }}{{cite journal | vauthors = Ford AC, Quigley EM, Lacy BE, Lembo AJ, Saito YA, Schiller LR, Soffer EE, Spiegel BM, Moayyedi P | s2cid = 205100444 | title = Effect of antidepressants and psychological therapies, including hypnotherapy, in irritable bowel syndrome: systematic review and meta-analysis | journal = The American Journal of Gastroenterology | volume = 109 | issue = 9 | pages = 1350–65; quiz 1366 | date = September 2014 | pmid = 24935275 | doi = 10.1038/ajg.2014.148 }}

FODMAPs are short-chain carbohydrates that are poorly absorbed in the small intestine. A 2018 systematic review found that although there is evidence of improved IBS symptoms with a low-FODMAP diet, the evidence is of very low quality.{{cite journal | vauthors = Dionne J, Ford AC, Yuan Y, Chey WD, Lacy BE, Saito YA, Quigley EM, Moayyedi P | s2cid = 50786768 | title = A Systematic Review and Meta-Analysis Evaluating the Efficacy of a Gluten-Free Diet and a Low FODMAPs Diet in Treating Symptoms of Irritable Bowel Syndrome | journal = The American Journal of Gastroenterology | volume = 113 | issue = 9 | pages = 1290–1300 | date = September 2018 | pmid = 30046155 | doi = 10.1038/s41395-018-0195-4 | url = http://eprints.whiterose.ac.uk/134755/ }} Symptoms most likely to improve on this type of diet include urgency, flatulence, bloating,Pessarelli, T., Sorge, A., Elli, L., & Costantino, A. The Gluten-free Diet and the Low-FODMAP Diet in the Management of Functional Abdominal Bloating and Distension. Frontiers in Nutrition, 2680. abdominal pain, and altered stool output. One national guideline advises a low FODMAP diet for managing IBS when other dietary and lifestyle measures have been unsuccessful. The diet restricts various carbohydrates which are poorly absorbed in the small intestine, as well as fructose and lactose, which are similarly poorly absorbed in those with intolerances to them. Reduction of fructose and fructan has been shown to reduce IBS symptoms in a dose-dependent manner in people with fructose malabsorption and IBS.{{cite journal | vauthors = Fedewa A, Rao SS | title = Dietary fructose intolerance, fructan intolerance and FODMAPs | journal = Current Gastroenterology Reports | volume = 16 | issue = 1 | page = 370 | date = January 2014 | pmid = 24357350 | pmc = 3934501 | doi = 10.1007/s11894-013-0370-0 }}

FODMAPs are fermentable oligo-, di-, monosaccharides and polyols, which are poorly absorbed in the small intestine and subsequently fermented by the bacteria in the distal small and proximal large intestine. This is a normal phenomenon, common to everyone. The resultant production of gas potentially results in bloating and flatulence.{{cite journal | vauthors = Gibson PR, Shepherd SJ | s2cid = 20666740 | title = Evidence-based dietary management of functional gastrointestinal symptoms: The FODMAP approach | journal = Journal of Gastroenterology and Hepatology | volume = 25 | issue = 2 | pages = 252–8 | date = February 2010 | pmid = 20136989 | doi = 10.1111/j.1440-1746.2009.06149.x | doi-access = free }} Although FODMAPs can produce certain digestive discomfort in some people, not only do they not cause intestinal inflammation, but they help avoid it, because they produce beneficial alterations in the intestinal flora that contribute to maintaining the good health of the colon.{{cite journal | vauthors = Makharia A, Catassi C, Makharia GK | title = The Overlap between Irritable Bowel Syndrome and Non-Celiac Gluten Sensitivity: A Clinical Dilemma | journal = Nutrients | volume = 7 | issue = 12 | pages = 10417–26 | date = December 2015 | pmid = 26690475 | pmc = 4690093 | doi = 10.3390/nu7125541 | type = Review | doi-access = free }}{{cite journal | vauthors = Greer JB, O'Keefe SJ | title = Microbial induction of immunity, inflammation, and cancer | journal = Frontiers in Physiology | volume = 1 | page = 168 | year = 2011 | pmid = 21423403 | pmc = 3059938 | doi = 10.3389/fphys.2010.00168 | type = Review | doi-access = free }}{{cite journal | vauthors = Andoh A, Tsujikawa T, Fujiyama Y | title = Role of dietary fiber and short-chain fatty acids in the colon | journal = Current Pharmaceutical Design | volume = 9 | issue = 4 | pages = 347–58 | year = 2003 | pmid = 12570825 | doi = 10.2174/1381612033391973 | type = Review }} FODMAPs are not the cause of irritable bowel syndrome nor other functional gastrointestinal disorders, but rather a person develops symptoms when the underlying bowel response is exaggerated or abnormal.

A low-FODMAP diet consists of restricting them from the diet. They are globally trimmed, rather than individually, which is more successful than for example restricting only fructose and fructans, which are also FODMAPs, as is recommended for those with fructose malabsorption.

A low-FODMAP diet might help to improve short-term digestive symptoms in adults with irritable bowel syndrome,{{cite journal | vauthors = Turco R, Salvatore S, Miele E, Romano C, Marseglia GL, Staiano A | title = Does a low FODMAPs diet reduce symptoms of functional abdominal pain disorders? A systematic review in adult and paediatric population, on behalf of Italian Society of Pediatrics | journal = Italian Journal of Pediatrics | volume = 44 | issue = 1 | page = 53 | date = May 2018 | pmid = 29764491 | pmc = 5952847 | doi = 10.1186/s13052-018-0495-8 | type = Systematic Review | doi-access = free }}{{cite journal | vauthors = Staudacher HM, Irving PM, Lomer MC, Whelan K | s2cid = 23001679 | title = Mechanisms and efficacy of dietary FODMAP restriction in IBS | journal = Nature Reviews. Gastroenterology & Hepatology | volume = 11 | issue = 4 | pages = 256–66 | date = April 2014 | pmid = 24445613 | doi = 10.1038/nrgastro.2013.259 | type = Review | quote = An emerging body of research now demonstrates the efficacy of fermentable carbohydrate restriction in IBS. [...] However, further work is urgently needed both to confirm clinical efficacy of fermentable carbohydrate restriction in a variety of clinical subgroups and to fully characterize the effect on the gut microbiota and the colonic environ¬ment. Whether the effect on luminal bifidobacteria is clinically relevant, preventable, or long lasting, needs to be investigated. The influence on nutrient intake, dietary diversity, which might also affect the gut microbiota,137 and quality of life also requires further exploration as does the possible economic effects due to reduced physician contact and need for medication. Although further work is required to confirm its place in IBS and functional bowel disorder clinical pathways, fermentable carbohydrate restriction is an important consideration for future national and international IBS guidelines. }}{{cite journal | vauthors = Marsh A, Eslick EM, Eslick GD | s2cid = 206969839 | title = Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta-analysis | journal = European Journal of Nutrition | volume = 55 | issue = 3 | pages = 897–906 | date = April 2016 | pmid = 25982757 | doi = 10.1007/s00394-015-0922-1 }}{{cite journal | vauthors = Rao SS, Yu S, Fedewa A | title = Systematic review: dietary fibre and FODMAP-restricted diet in the management of constipation and irritable bowel syndrome | journal = Alimentary Pharmacology & Therapeutics | volume = 41 | issue = 12 | pages = 1256–70 | date = June 2015 | pmid = 25903636 | doi = 10.1111/apt.13167 | s2cid = 27558785 | doi-access = free }} but its long-term follow-up can have negative effects because it causes a detrimental impact on the gut microbiota and metabolome.{{cite journal | vauthors = Tuck CJ, Muir JG, Barrett JS, Gibson PR | s2cid = 28811344 | title = Fermentable oligosaccharides, disaccharides, monosaccharides and polyols: role in irritable bowel syndrome | journal = Expert Review of Gastroenterology & Hepatology | volume = 8 | issue = 7 | pages = 819–34 | date = September 2014 | pmid = 24830318 | doi = 10.1586/17474124.2014.917956 }}{{cite journal | vauthors = Heiman ML, Greenway FL | title = A healthy gastrointestinal microbiome is dependent on dietary diversity | journal = Molecular Metabolism | volume = 5 | issue = 5 | pages = 317–320 | date = May 2016 | pmid = 27110483 | pmc = 4837298 | doi = 10.1016/j.molmet.2016.02.005 | type = Review }} It should only be used for short periods of time and under the advice of a specialist.{{cite journal | vauthors = Staudacher HM, Whelan K | s2cid = 3492917 | title = The low FODMAP diet: recent advances in understanding its mechanisms and efficacy in IBS | journal = Gut | volume = 66 | issue = 8 | pages = 1517–1527 | date = August 2017 | pmid = 28592442 | doi = 10.1136/gutjnl-2017-313750 | url = https://kclpure.kcl.ac.uk/portal/en/publications/the-low-fodmap-diet(c7f6c885-e206-4fa4-8206-576e70bd3d59).html | type = Review }} A low-FODMAP diet is highly restrictive in various groups of nutrients and can be impractical to follow in the long-term.{{cite journal | vauthors = Hou JK, Lee D, Lewis J | title = Diet and inflammatory bowel disease: review of patient-targeted recommendations | journal = Clinical Gastroenterology and Hepatology | volume = 12 | issue = 10 | pages = 1592–600 | date = October 2014 | pmid = 24107394 | pmc = 4021001 | doi = 10.1016/j.cgh.2013.09.063 | type = Review | quote = Even less evidence exists for the efficacy of the SCD, FODMAP, or Paleo diet. Furthermore, the practicality of maintaining these interventions over long periods of time is doubtful. At a practical level, adherence to defined diets may result in an unnecessary financial burden or reduction in overall caloric intake in people who are already at risk for protein-calorie malnutrition. }} More studies are needed to assess the true impact of this diet on health.

In addition, the use of a low-FODMAP diet without verifying the diagnosis of IBS may result in misdiagnosis of other conditions such as celiac disease.{{cite journal | vauthors = Barrett JS | s2cid = 24990614 | title = How to institute the low-FODMAP diet | journal = Journal of Gastroenterology and Hepatology | volume = 32 | issue = Suppl 1 | pages = 8–10 | date = March 2017 | pmid = 28244669 | doi = 10.1111/jgh.13686 | type = Review | quote = Common symptoms of IBS are bloating, abdominal pain, excessive flatus, constipation, diarrhea, or alternating bowel habit. These symptoms, however, are also common in the presentation of coeliac disease, inflammatory bowel disease, defecatory disorders, and colon cancer. Confirming the diagnosis is crucial so that appropriate therapy can be undertaken. Unfortunately, even in these alternate diagnoses, a change in diet restricting FODMAPs may improve symptoms and mask the fact that the correct diagnosis has not been made. This is the case with coeliac disease where a low-FODMAP diet can concurrently reduce dietary gluten, improving symptoms, and also affecting coeliac diagnostic indices.3,4 Misdiagnosis of intestinal diseases can lead to secondary problems such as nutritional deficiencies, cancer risk, or even mortality in the case of colon cancer. | doi-access = free }} Since the consumption of gluten is suppressed or reduced with a low-FODMAP diet, the improvement of the digestive symptoms with this diet may not be related to the withdrawal of the FODMAPs, but of gluten, indicating the presence of unrecognized celiac disease, avoiding its diagnosis and correct treatment, with the consequent risk of several serious health complications, including various types of cancer.{{cite web|url=http://www.worldgastroenterology.org/guidelines/global-guidelines/celiac-disease/celiac-disease-english|title=Celiac disease|date=July 2016|publisher=World Gastroenterology Organisation Global Guidelines|access-date=4 June 2018|url-status=dead|archive-url=https://web.archive.org/web/20170317123604/http://www.worldgastroenterology.org/guidelines/global-guidelines/celiac-disease/celiac-disease-english|archive-date=March 17, 2017|df=dmy-all}}

Soluble fiber supplementation (e.g., psyllium/ispagula husk) may be effective in improving symptoms. However soluble fiber does not appear to reduce pain. It acts as a bulking agent, and for many people with IBS-D, allows for a more consistent stool. For people with IBS-C, it seems to allow for a softer, moister, more easily passable stool.{{citation needed|date=June 2021}}

However, insoluble fiber (e.g., bran) is not effective for IBS.{{cite journal | vauthors = Francis CY, Whorwell PJ | s2cid = 34156816 | title = Bran and irritable bowel syndrome: time for reappraisal | journal = Lancet | volume = 344 | issue = 8914 | pages = 39–40 | date = July 1994 | pmid = 7912305 | doi = 10.1016/S0140-6736(94)91055-3 }} In some people, insoluble fiber supplementation may aggravate symptoms.{{cite journal | vauthors = Bijkerk CJ, de Wit NJ, Muris JW, Whorwell PJ, Knottnerus JA, Hoes AW | title = Soluble or insoluble fibre in irritable bowel syndrome in primary care? Randomised placebo controlled trial | journal = BMJ | volume = 339 | issue = b3154 | pages = b3154 | date = August 2009 | pmid = 19713235 | pmc = 3272664 | doi = 10.1136/bmj.b3154 }}{{cite journal | vauthors = Ducrotté P | title = [Irritable bowel syndrome: current treatment options] | journal = Presse Médicale | volume = 36 | issue = 11 Pt 2 | pages = 1619–26 | date = November 2007 | pmid = 17490849 | doi = 10.1016/j.lpm.2007.03.008 }}

Fiber might be beneficial in those who have a predominance of constipation. In people who have IBS-C, soluble fiber can reduce overall symptoms but will not reduce pain. The research supporting dietary fiber contains conflicting small studies complicated by the heterogeneity of types of fiber and doses used.{{cite journal | vauthors = Bijkerk CJ, Muris JW, Knottnerus JA, Hoes AW, de Wit NJ | s2cid = 38345912 | title = Systematic review: the role of different types of fibre in the treatment of irritable bowel syndrome | journal = Alimentary Pharmacology & Therapeutics | volume = 19 | issue = 3 | pages = 245–51 | date = February 2004 | pmid = 14984370 | doi = 10.1111/j.0269-2813.2004.01862.x }}

Physical activity can have beneficial effects on irritable bowel syndrome.{{cite journal | doi=10.1016/j.dld.2022.08.034 | title=A practical guide to the proper prescription of physical activity in patients with irritable bowel syndrome | date=2022 | journal=Digestive and Liver Disease | volume=54 | issue=11 | pages=1600–1604 | pmid=36153192 | vauthors = Costantino A, Pessarelli T, Vecchiato M, Vecchi M, Basilisco G, Ermolao A }} In light of this, the latest British Society of Gastroenterology guidelines on the management of IBS have stated that all patients with IBS should be advised to take regular exercise (strong recommendation, weak certainty evidence),{{cite journal | doi=10.1136/gutjnl-2021-324598 | title=British Society of Gastroenterology guidelines on the management of irritable bowel syndrome | date=2021 | journal=Gut | volume=70 | issue=7 | pages=1214–1240 | pmid=33903147 | vauthors = Vasant DH, Paine PA, Black CJ, Houghton LA, Everitt HA, Corsetti M, Agrawal A, Aziz I, Farmer AD, Eugenicos MP, Moss-Morris R, Yiannakou Y, Ford AC }} whereas the American College of Gastroenterology guidelines have suggested with a lower certainty of evidence.{{cite journal | doi=10.14309/ajg.0000000000001036 | title=ACG Clinical Guideline: Management of Irritable Bowel Syndrome | date=2021 | journal=American Journal of Gastroenterology | volume=116 | issue=1 | pages=17–44 | pmid=33315591 | vauthors = Lacy BE, Pimentel M, Brenner DM, Chey WD, Keefer LA, Long MD, Moshiree B }} Physical activity could significantly improve people’s adherence and, consequently, lead to a significant clinical benefit for symptoms of irritable bowel syndrome.

Medications that may be useful include antispasmodics such as dicyclomine and antidepressants.{{cite journal | vauthors = Ruepert L, Quartero AO, de Wit NJ, van der Heijden GJ, Rubin G, Muris JW | title = Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome | journal = The Cochrane Database of Systematic Reviews | issue = 8 | pages = CD003460 | date = August 2011 | volume = 2013 | pmid = 21833945 | doi = 10.1002/14651858.CD003460.pub3 | pmc = 8745618 | s2cid = 22977015 }} Both H1-antihistamines and mast cell stabilizers have shown efficacy in reducing pain associated with visceral hypersensitivity in IBS.

A number of 5-HT3 antagonists or 5-HT4 agonists were proposed clinically to treat diarrhea-predominant IBS and constipation-predominant IBS, respectively. However, severe side effects have resulted in its withdrawal by Food and Drug Administration and are now prescribed under emergency investigational drug protocol.{{cite journal | vauthors = Ford AC, Brandt LJ, Young C, Chey WD, Foxx-Orenstein AE, Moayyedi P | title = Efficacy of 5-HT3 antagonists and 5-HT4 agonists in irritable bowel syndrome: systematic review and meta-analysis | journal = American Journal of Gastroenterology | year = 2009 | volume = 104 | issue = 7 | pages = 1831–1843 | pmid = 19471254 | doi = 10.1038/ajg.2009.223 | s2cid = 8042629 }} Other 5-HT receptor subtypes, such as 5-HT7 receptor, have yet to be developed.

For people who do not adequately respond to dietary fiber, osmotic laxatives such as polyethylene glycol, sorbitol, and lactulose can help avoid "cathartic colon" which has been associated with stimulant laxatives.{{cite journal | vauthors = Joo JS, Ehrenpreis ED, Gonzalez L, Kaye M, Breno S, Wexner SD, Zaitman D, Secrest K | title = Alterations in colonic anatomy induced by chronic stimulant laxatives: the cathartic colon revisited | journal = Journal of Clinical Gastroenterology | volume = 26 | issue = 4 | pages = 283–6 | date = June 1998 | pmid = 9649012 | doi = 10.1097/00004836-199806000-00014 }} Lubiprostone is a gastrointestinal agent used for the treatment of constipation-predominant IBS.

• {{cite journal | vauthors = Li F, Fu T, Tong WD, Liu BH, Li CX, Gao Y, Wu JS, Wang XF, Zhang AP | title = Lubiprostone Is Effective in the Treatment of Chronic Idiopathic Constipation and Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials | journal = Mayo Clinic Proceedings | volume = 91 | issue = 4 | pages = 456–468 | date = April 2016 | pmid = 27046523 | doi = 10.1016/j.mayocp.2016.01.015 | quote = Lubiprostone is a safe and efficacious drug for the treatment of chronic idiopathic constipation and irritable bowel syndrome with constipation, with limited adverse effects in 3 months of follow-up. }}
• {{cite web |title=Lubiprostone: MedlinePlus Drug Information |url=https://medlineplus.gov/druginfo/meds/a607034.html |website=medlineplus.gov |date=2017 |quote=Lubiprostone is also used to treat irritable bowel syndrome with constipation... in women who are at least 18 years of age.}}
• {{cite web |title=Lubiprostone Oral: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing - WebMD |url=https://www.webmd.com/drugs/2/drug-95017/lubiprostone-oral/details |website=www.webmd.com}}
• {{cite web |title=Lubiprostone (Oral Route) Side Effects - Mayo Clinic |url=https://www.mayoclinic.org/drugs-supplements/lubiprostone-oral-route/side-effects/drg-20069057?p=1 |website=www.mayoclinic.org |date=2021}}

The use of antispasmodic drugs (e.g., anticholinergics such as hyoscyamine or dicyclomine) may help people who have cramps or diarrhea. A meta-analysis by the Cochrane Collaboration concludes that one out of seven people benefit from treatment with antispasmodics. Antispasmodics can be divided into two groups: neurotropics and musculotropics. Musculotropics, such as mebeverine, act directly at the smooth muscle of the gastrointestinal tract, relieving spasm without affecting normal gut motility.{{Citation needed|date=January 2009}} Since this action is not mediated by the autonomic nervous system, the usual anticholinergic side effects are absent.{{cite book| vauthors = Barber P, Parkes J, Blundell D |title=Further Essentials of Pharmacology for Nurses|url=https://books.google.com/books?id=BjhFBgAAQBAJ&pg=PA34|date=1 June 2012|publisher=McGraw-Hill Education (UK)|isbn=978-0-335-24398-3|pages=34–|url-status=live|archive-url=https://web.archive.org/web/20170216212139/https://books.google.com/books?id=BjhFBgAAQBAJ&pg=PA34|archive-date=February 16, 2017|df=mdy-all}} The antispasmodic otilonium may also be useful.{{cite journal | vauthors = Annaházi A, Róka R, Rosztóczy A, Wittmann T | title = Role of antispasmodics in the treatment of irritable bowel syndrome | journal = World Journal of Gastroenterology | volume = 20 | issue = 20 | pages = 6031–43 | date = May 2014 | pmid = 24876726 | pmc = 4033443 | doi = 10.3748/wjg.v20.i20.6031 | doi-access = free }}

Proton-pump inhibitors (PPIs) used to suppress stomach acid production may cause small intestinal bacterial overgrowth (SIBO) leading to IBS symptoms.{{cite journal | vauthors = Ghoshal UC, Shukla R, Ghoshal U | title = Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy | journal = Gut and Liver | volume = 11 | issue = 2 | pages = 196–208 | date = March 2017 | pmid = 28274108 | pmc = 5347643 | doi = 10.5009/gnl16126 }} Discontinuation of PPIs in selected individuals has been recommended as it may lead to an improvement or resolution of IBS symptoms.{{cite journal | vauthors = Simrén M, Barbara G, Flint HJ, Spiegel BM, Spiller RC, Vanner S, Verdu EF, Whorwell PJ, Zoetendal EG | title = Intestinal microbiota in functional bowel disorders: a Rome foundation report | journal = Gut | volume = 62 | issue = 1 | pages = 159–76 | date = January 2013 | pmid = 22730468 | pmc = 3551212 | doi = 10.1136/gutjnl-2012-302167 }}

Evidence is conflicting about the benefit of antidepressants in IBS. Some meta-analyses have found a benefit, while others have not.{{cite web| vauthors = Wald A | veditors = Talley NJ, Grover S |title=Treatment of irritable bowel syndrome in adults|url= http://www.uptodate.com/online/content/topic.do?topicKey=gi_dis/5811&selectedTitle=1~148&source=search_result#9 |url-access=subscription|work=UpToDate Inc. }} There is good evidence that low doses of tricyclic antidepressants (TCAs) can be effective for IBS.{{cite journal | vauthors = Ford AC, Lacy BE, Harris LA, Quigley EM, Moayyedi P | title = Effect of Antidepressants and Psychological Therapies in Irritable Bowel Syndrome: An Updated Systematic Review and Meta-Analysis | journal = The American Journal of Gastroenterology | volume = 114 | issue = 1 | pages = 21–39 | date = January 2019 | pmid = 30177784 | doi = 10.1038/s41395-018-0222-5 | url = http://eprints.whiterose.ac.uk/135430/2/AJG-18-087R1%20CLEAN.pdf | s2cid = 52151689 }} With TCAs, about one in three people improve.{{cite journal|vauthors=Jackson JL, O'Malley PG, Tomkins G, Balden E, Santoro J, Kroenke K|date=January 2000|title=Treatment of functional gastrointestinal disorders with antidepressant medications: a meta-analysis|journal=The American Journal of Medicine|volume=108|issue=1|pages=65–72|doi=10.1016/S0002-9343(99)00299-5|pmid=11059442}}

However, the evidence is less robust for the effectiveness of other antidepressant classes such as selective serotonin reuptake inhibitor antidepressants (SSRIs). Because of their serotonergic effect, SSRIs have been studied in IBS, especially for people who are constipation predominant. As of 2015, the evidence indicates that SSRIs do not help.{{cite journal | vauthors = Xie C, Tang Y, Wang Y, Yu T, Wang Y, Jiang L, Lin L | title = Efficacy and Safety of Antidepressants for the Treatment of Irritable Bowel Syndrome: A Meta-Analysis | journal = PLOS ONE | volume = 10 | issue = 8 | pages = e0127815 | date = 7 August 2015 | pmid = 26252008 | pmc = 4529302 | doi = 10.1371/journal.pone.0127815 | bibcode = 2015PLoSO..1027815X | doi-access = free }} Antidepressants are not effective for IBS in people with depression, possibly because lower doses of antidepressants than the doses used to treat depression are required for relief of IBS.{{cite journal | vauthors = Song KH, Jung HK, Kim HJ, Koo HS, Kwon YH, Shin HD, Lim HC, Shin JE, Kim SE, Cho DH, Kim JH, Kim HJ | title = Clinical Practice Guidelines for Irritable Bowel Syndrome in Korea, 2017 Revised Edition | journal = Journal of Neurogastroenterology and Motility | volume = 24 | issue = 2 | pages = 197–215 | date = April 2018 | pmid = 29605976 | pmc = 5885719 | doi = 10.5056/jnm17145 }}

Magnesium aluminum silicates and alverine citrate drugs can be effective for IBS.{{cite journal | vauthors = Lee KJ | title = Pharmacologic Agents for Chronic Diarrhea | journal = Intestinal Research | volume = 13 | issue = 4 | pages = 306–12 | date = October 2015 | pmid = 26576135 | pmc = 4641856 | doi = 10.5217/ir.2015.13.4.306 }}

Rifaximin may be useful as a treatment for IBS symptoms, including abdominal bloating and flatulence, although relief of abdominal distension is delayed.{{cite journal | vauthors = Ford AC, Harris LA, Lacy BE, Quigley EM, Moayyedi P | s2cid = 52933693 | title = Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome | journal = Alimentary Pharmacology & Therapeutics | volume = 48 | issue = 10 | pages = 1044–1060 | date = November 2018 | pmid = 30294792 | doi = 10.1111/apt.15001 | doi-access = free }} It is especially useful where small intestinal bacterial overgrowth is involved.

In individuals with IBS and low levels of vitamin D, supplementation is recommended. Some evidence suggests that vitamin D supplementation may improve symptoms of IBS, but further research is needed before it can be recommended as a specific treatment for IBS.

There is inconsistent evidence from studies with poor methodological quality that psychological therapies can be effective in the treatment of IBS. Preliminary research shows that psychotherapeutic interventions are correlated with reductions in both autonomic nervous system dysregulation and gastrointestinal symptoms. Reducing stress may also reduce the frequency and severity of IBS symptoms. Techniques that may be helpful include regular exercise, such as swimming, walking, or running.{{cite web |url=http://www.nhs.uk/Conditions/Irritable-bowel-syndrome/Pages/Treatment.aspx |title=Irritable Bowel Syndrome (IBS) – Treatment |work= NHS Choices |publisher=National Health Service |access-date=2012-10-21 |url-status=live |archive-url=https://web.archive.org/web/20121018175323/http://www.nhs.uk/Conditions/Irritable-bowel-syndrome/Pages/Treatment.aspx |archive-date=October 18, 2012 |df=mdy-all }}

Probiotics can be beneficial in the treatment of IBS; taking 10 billion to 100 billion beneficial bacteria per day is recommended for beneficial results. However, further research is needed on individual strains of beneficial bacteria for more refined recommendations.{{cite journal | vauthors = Nikfar S, Rahimi R, Rahimi F, Derakhshani S, Abdollahi M | s2cid = 42964491 | title = Efficacy of probiotics in irritable bowel syndrome: a meta-analysis of randomized, controlled trials | journal = Diseases of the Colon and Rectum | volume = 51 | issue = 12 | pages = 1775–80 | date = December 2008 | pmid = 18465170 | doi = 10.1007/s10350-008-9335-z }} Probiotics have positive effects such as enhancing the intestinal mucosal barrier, providing a physical barrier, bacteriocin production (resulting in reduced numbers of pathogenic and gas-producing bacteria), reducing intestinal permeability and bacterial translocation, and regulating the immune system both locally and systemically among other beneficial effects. Probiotics may also have positive effects on the gut–brain axis by their positive effects countering the effects of stress on gut immunity and gut function.{{cite journal | vauthors = Konturek PC, Brzozowski T, Konturek SJ | title = Stress and the gut: pathophysiology, clinical consequences, diagnostic approach and treatment options | journal = Journal of Physiology and Pharmacology | volume = 62 | issue = 6 | pages = 591–9 | date = December 2011 | pmid = 22314561 }}

A number of probiotics have been found to be effective, including Lactobacillus plantarum, and Bifidobacteria infantis;{{cite press release |url=http://www.acg.gi.org/media/releases/ACG05Release_ProbioticsinIBS.pdf |title=New Studies Examine the Evidence on Probiotics in IBS |publisher=American College of Gastroenterology |date=October 31, 2005 |url-status=dead |archive-url=https://web.archive.org/web/20060210062320/http://www.acg.gi.org/media/releases/ACG05Release_ProbioticsinIBS.pdf |archive-date=February 10, 2006 |df=mdy-all }} but one review found only Bifidobacteria infantis showed efficacy.{{cite journal | vauthors = Brenner DM, Moeller MJ, Chey WD, Schoenfeld PS | s2cid = 24789648 | title = The utility of probiotics in the treatment of irritable bowel syndrome: a systematic review | journal = The American Journal of Gastroenterology | volume = 104 | issue = 4 | pages = 1033–49; quiz 1050 | date = April 2009 | pmid = 19277023 | doi = 10.1038/ajg.2009.25 }} B. infantis may have effects beyond the gut via it causing a reduction of proinflammatory cytokine activity and elevation of blood tryptophan levels, which may cause an improvement in symptoms of depression.{{cite journal | vauthors = Aragon G, Graham DB, Borum M, Doman DB | title = Probiotic therapy for irritable bowel syndrome | journal = Gastroenterology & Hepatology | volume = 6 | issue = 1 | pages = 39–44 | date = January 2010 | pmid = 20567539 | pmc = 2886445 }} Some yogurt is made using probiotics that may help ease symptoms of IBS.{{cite web |url=http://www.mayoclinic.com/health/ibs-diet/AN01346 |title=IBS diet: Can yogurt ease symptoms? |work=Mayo Clinic |date=May 21, 2008 |url-status=live |archive-url=https://web.archive.org/web/20100209073302/http://www.mayoclinic.com/health/ibs-diet/AN01346 |archive-date=February 9, 2010 |df=mdy-all }} A probiotic yeast called Saccharomyces boulardii has some evidence of effectiveness in the treatment of irritable bowel syndrome.{{cite journal | vauthors = McFarland LV | title = Systematic review and meta-analysis of Saccharomyces boulardii in adult patients | journal = World Journal of Gastroenterology | volume = 16 | issue = 18 | pages = 2202–22 | date = May 2010 | pmid = 20458757 | pmc = 2868213 | doi = 10.3748/wjg.v16.i18.2202 | doi-access = free }}

Certain probiotics have different effects on certain symptoms of IBS. For example, Bifidobacterium breve, B. longum, and Lactobacillus acidophilus have been found to alleviate abdominal pain. B. breve, B. infantis, L. casei, or L. plantarum species alleviated distension symptoms. B. breve, B. infantis, L. casei, L. plantarum, B. longum, L. acidophilus, L. bulgaricus, and Streptococcus salivarius ssp. thermophilus have all been found to affect flatulence levels. Most clinical studies show probiotics do not improve straining, sense of incomplete evacuation, stool consistency, fecal urgency, or stool frequency, although a few clinical studies did find some benefit of probiotic therapy. The evidence is conflicting for whether probiotics improve overall quality of life scores.{{cite journal | vauthors = Ortiz-Lucas M, Tobías A, Saz P, Sebastián JJ | title = Effect of probiotic species on irritable bowel syndrome symptoms: A bring up to date meta-analysis | journal = Revista Española de Enfermedades Digestivas| volume = 105 | issue = 1 | pages = 19–36 | date = January 2013 | pmid = 23548007 | doi = 10.4321/s1130-01082013000100005 | url = http://scielo.isciii.es/pdf/diges/v105n1/original4.pdf }}

Probiotics may exert their beneficial effects on IBS symptoms via preserving the gut microbiota, normalisation of cytokine blood levels, improving the intestinal transit time, decreasing small intestine permeability, and by treating small intestinal bacterial overgrowth of fermenting bacteria. A fecal transplant does not appear useful as of 2019.{{cite journal | vauthors = Xu D, Chen VL, Steiner CA, Berinstein JA, Eswaran S, Waljee AK, Higgins PD, Owyang C | title = Efficacy of Fecal Microbiota Transplantation in Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis | journal = The American Journal of Gastroenterology | volume = 114 | issue = 7 | pages = 1043–1050 | date = July 2019 | pmid = 30908299 | pmc = 7257434 | doi = 10.14309/ajg.0000000000000198 }}

Peppermint oil appears useful.{{cite journal | vauthors = Wilkins T, Pepitone C, Alex B, Schade RR | title = Diagnosis and management of IBS in adults | journal = American Family Physician | volume = 86 | issue = 5 | pages = 419–26 | date = September 2012 | pmid = 22963061 }} In a meta-analysis it was found to be superior to placebo for improvement of IBS symptoms, at least in the short term.{{cite journal | vauthors = Khanna R, MacDonald JK, Levesque BG | s2cid = 22520810 | title = Peppermint oil for the treatment of irritable bowel syndrome: a systematic review and meta-analysis | journal = Journal of Clinical Gastroenterology | volume = 48 | issue = 6 | pages = 505–12 | date = July 2014 | pmid = 24100754 | doi = 10.1097/MCG.0b013e3182a88357 }} An earlier meta-analysis suggested the results of peppermint oil were tentative as the number of people studied was small and blinding of those receiving treatment was unclear. Safety during pregnancy has not been established, however, and caution is required not to chew or break the enteric coating; otherwise, gastroesophageal reflux may occur as a result of lower esophageal sphincter relaxation. Occasionally, nausea and perianal burning occur as side effects. Iberogast, a multi-herbal extract, was found to be superior in efficacy to placebo.{{cite journal | vauthors = Rösch W, Liebregts T, Gundermann KJ, Vinson B, Holtmann G | title = Phytotherapy for functional dyspepsia: a review of the clinical evidence for the herbal preparation STW 5 | journal = Phytomedicine | volume = 13 |issue=Suppl 5 | pages = 114–21 | year = 2006 | pmid = 16978851 | doi = 10.1016/j.phymed.2006.03.022 }} A comprehensive meta-analysis using twelve random trials resulted that the use of peppermint oil is an effective therapy for adults with irritable bowel syndrome.{{cite journal | vauthors = Alammar N, Wang L, Saberi B, Nanavati J, Holtmann G, Shinohara RT, Mullin GE | title = The impact of peppermint oil on the irritable bowel syndrome: a meta-analysis of the pooled clinical data | journal = BMC Complementary and Alternative Medicine | volume = 19 | issue = 1 | page = 21 | date = January 2019 | pmid = 30654773 | pmc = 6337770 | doi = 10.1186/s12906-018-2409-0 | doi-access = free }}

Research into cannabinoids as treatment for IBS is limited. GI propulsion, secretion, and inflammation in the gut are all modulated by the ECS (Endocannabinoid system), providing a rationale for cannabinoids as treatment candidates for IBS.{{cite journal | vauthors = Russo EB | title = Clinical Endocannabinoid Deficiency Reconsidered: Current Research Supports the Theory in Migraine, Fibromyalgia, Irritable Bowel, and Other Treatment-Resistant Syndromes | journal = Cannabis and Cannabinoid Research | volume = 1 | issue = 1 | pages = 154–165 | date = 2016-07-01 | pmid = 28861491 | pmc = 5576607 | doi = 10.1089/can.2016.0009 }}

Only limited evidence exists for the effectiveness of other herbal remedies for IBS. As with all herbs, it is wise to be aware of possible drug interactions and adverse effects.{{cite journal | vauthors = Shen YH, Nahas R | title = Complementary and alternative medicine for treatment of irritable bowel syndrome | journal = Canadian Family Physician | volume = 55 | issue = 2 | pages = 143–8 | date = February 2009 | pmid = 19221071 | pmc = 2642499 }}

There are no benefits of acupuncture compared to placebo for IBS symptom severity or IBS-related quality of life.{{cite journal |vauthors=Manheimer E, Cheng K, Wieland LS, Min LS, Shen X, Berman BM, Lao L |date=May 2012 |title=Acupuncture for treatment of irritable bowel syndrome |journal=The Cochrane Database of Systematic Reviews |volume=2012 |issue=5 |pages=CD005111 |doi=10.1002/14651858.CD005111.pub3 |pmc=3718572 |pmid=22592702}}

File:Ibs prevalence.svg

The prevalence of IBS varies by country and by age range examined. The bar graph at right shows the percentage of the population reporting symptoms of IBS in studies from various geographic regions (see table below for references). The following table contains a list of studies performed in different countries that measured the prevalence of IBS and IBS-like symptoms:

In Western countries, women are around two to three times more likely to be diagnosed with IBS and four to five times more likely to seek specialty care for it than men.{{cite journal | vauthors = Payne S | title = Sex, gender, and irritable bowel syndrome: making the connections | journal = Gender Medicine | volume = 1 | issue = 1 | pages = 18–28 | date = August 2004 | pmid = 16115580 | doi = 10.1016/S1550-8579(04)80007-X }} However, women in East Asian countries are not more likely than men to have irritable bowel syndrome, and there are conflicting reports about the female predominance of the disease in Africa and other parts of Asia.{{cite journal | vauthors = Kang JY | title = Systematic review: the influence of geography and ethnicity in irritable bowel syndrome | journal = Alimentary Pharmacology & Therapeutics | volume = 21 | issue = 6 | pages = 663–676 | date = March 2005 | pmid = 15771752 | doi = 10.1111/j.1365-2036.2005.02396.x | s2cid = 25990902 | doi-access = free }} "A number of African and Asian authors have reported that the female predominance typical of western patients did not occur.5, 6, 8, 9, 12-16 Again, other authors did not concur with this finding.10" People diagnosed with IBS are usually younger than 45 years old. Studies of females with IBS show symptom severity often fluctuates with the menstrual cycle, suggesting hormonal differences may play a role.{{cite journal | vauthors = Jackson NA, Houghton LA, Whorwell PJ, Currer B | title = Does the menstrual cycle affect anorectal physiology? | journal = Digestive Diseases and Sciences | volume = 39 | issue = 12 | pages = 2607–2611 | date = December 1994 | pmid = 7995186 | doi = 10.1007/bf02087697 | s2cid = 19400135 }} Endorsement of gender-related traits has been associated with quality of life and psychological adjustment in IBS.{{cite journal | vauthors = Voci SC, Cramer KM | title = Gender-related traits, quality of life, and psychological adjustment among women with irritable bowel syndrome | journal = Quality of Life Research | volume = 18 | issue = 9 | pages = 1169–1176 | date = November 2009 | pmid = 19728159 | doi = 10.1007/s11136-009-9532-9 | s2cid = 21629490 }} The increase in gastrointestinal symptoms during menses or early menopause may be related to declining or low estrogen and progesterone, suggesting that estrogen withdrawal may play a role in IBS.{{cite journal | vauthors = Heitkemper MM, Chang L | title = Do fluctuations in ovarian hormones affect gastrointestinal symptoms in women with irritable bowel syndrome? | journal = Gender Medicine | volume = 6 | issue = Suppl 2 | pages = 152–167 | date = 1 January 2009 | pmid = 19406367 | pmc = 3322543 | doi = 10.1016/j.genm.2009.03.004 }} Gender differences in healthcare-seeking may also play a role.{{cite journal | vauthors = Drossman DA, Li Z, Andruzzi E, Temple RD, Talley NJ, Thompson WG, Whitehead WE, Janssens J, Funch-Jensen P, Corazziari E | title = U.S. householder survey of functional gastrointestinal disorders. Prevalence, sociodemography, and health impact | journal = Digestive Diseases and Sciences | volume = 38 | issue = 9 | pages = 1569–1580 | date = September 1993 | pmid = 8359066 | doi = 10.1007/bf01303162 | s2cid = 37966231 }} Gender differences in trait anxiety may contribute to lower pain thresholds in women, putting them at greater risk for a number of chronic pain disorders.{{cite journal | vauthors = Goffaux P, Michaud K, Gaudreau J, Chalaye P, Rainville P, Marchand S | title = Sex differences in perceived pain are affected by an anxious brain | journal = Pain | volume = 152 | issue = 9 | pages = 2065–2073 | date = September 2011 | pmid = 21665365 | doi = 10.1016/j.pain.2011.05.002 | s2cid = 241921 }} Finally, sexual trauma is a major risk factor for IBS, as are other forms of abuse.{{cite journal | vauthors = Sansone RA, Sansone LA | title = IRRITABLE BOWEL SYNDROME: Relationships with Abuse in Childhood | journal = Innovations in Clinical Neuroscience | volume = 12 | issue = 5–6 | pages = 34–37 | date = 2012-05-02 | pmid = 26155376 | pmc = 4479362 }} Because women are at higher risk of sexual abuse than men, sex-related risk of abuse may contribute to the higher rate of IBS in women.{{cite journal | vauthors = Walker EA, Katon WJ, Roy-Byrne PP, Jemelka RP, Russo J | title = Histories of sexual victimization in patients with irritable bowel syndrome or inflammatory bowel disease | journal = The American Journal of Psychiatry | volume = 150 | issue = 10 | pages = 1502–1506 | date = October 1993 | pmid = 8379554 | doi = 10.1176/ajp.150.10.1502 | s2cid = 21976238 }}

The concept of an "irritable bowel" was introduced by P. W. Brown, first in The Journal of the Kansas Medical Society in 1947{{cite journal | vauthors = Brown PW | title = The irritable bowel syndrome | journal = The Journal of the Kansas Medical Society | volume = 48 | issue = 7 | pages = 309–312 | date = July 1947 | pmid = 20250197 | url = https://pubmed.ncbi.nlm.nih.gov/20250197/ }} and later in the Rocky Mountain Medical Journal in 1950.{{cite journal | vauthors = Brown PW | title = The irritable bowel syndrome | journal = Rocky Mountain Medical Journal | volume = 47 | issue = 5 | pages = 343–346 | date = May 1950 | pmid = 15418074 | url = https://pubmed.ncbi.nlm.nih.gov/15418074/ }} The term was used to categorize people who developed symptoms of diarrhea, abdominal pain, and constipation, but where no well-recognized infective cause could be found. Early theories suggested the irritable bowel was caused by a psychosomatic or mental disorder.{{cite journal | vauthors = Brown PW | title = The irritable bowel syndrome | journal = Rocky Mountain Medical Journal | volume = 47 | issue = 5 | pages = 343–346 | date = May 1950 | pmid = 15418074 }} World IBS Day was founded on April 19th, 2019 and is celebrated annually in order to raise awareness about Irritable Bowel Syndrome.{{Cite web |title=About Us |url=https://worldibsday.org |access-date=2025-03-26 |website=April 19, World IBS Day - Irritable Bowel Syndrome |language=en-US}} In some locations World IBS Day is also called World IBS Awareness Day. World Irritable Bowel Syndrome Day or simply IBS Awareness Day.{{Cite web |title=About Us |url=https://worldibsday.org/about/ |access-date=2025-03-26 |website=April 19, World IBS Day - Irritable Bowel Syndrome |language=en-US}}

{{Globalize|section|date=July 2019}}

The aggregate cost of irritable bowel syndrome in the United States has been estimated at $1.7–10 billion in direct medical costs, with an additional $20 billion in indirect costs, for a total of $21.7–30 billion. A study by a managed care company comparing medical costs for people with IBS to non-IBS controls identified a 49% annual increase in medical costs associated with a diagnosis of IBS.{{cite journal | vauthors = Levy RL, Von Korff M, Whitehead WE, Stang P, Saunders K, Jhingran P, Barghout V, Feld AD | title = Costs of care for irritable bowel syndrome patients in a health maintenance organization | journal = The American Journal of Gastroenterology | volume = 96 | issue = 11 | pages = 3122–9 | date = November 2001 | doi = 10.1111/j.1572-0241.2001.05258.x | pmid = 11721759 | s2cid = 31865692 }} People with IBS incurred average annual direct costs of $5,049 and $406 in out-of-pocket expenses in 2007.{{cite journal | vauthors = Nyrop KA, Palsson OS, Levy RL, Von Korff M, Feld AD, Turner MJ, Whitehead WE | title = Costs of health care for irritable bowel syndrome, chronic constipation, functional diarrhoea and functional abdominal pain | journal = Alimentary Pharmacology & Therapeutics | volume = 26 | issue = 2 | pages = 237–48 | date = July 2007 | pmid = 17593069 | doi = 10.1111/j.1365-2036.2007.03370.x | s2cid = 31374266 | doi-access = free }} A study of workers with IBS found that they reported a 34.6% loss in productivity, corresponding to 13.8 hours lost per 40 hour week.{{cite journal | vauthors = Paré P, Gray J, Lam S, Balshaw R, Khorasheh S, Barbeau M, Kelly S, McBurney CR | title = Health-related quality of life, work productivity, and health care resource utilization of subjects with irritable bowel syndrome: baseline results from LOGIC (Longitudinal Outcomes Study of Gastrointestinal Symptoms in Canada), a naturalistic study | journal = Clinical Therapeutics | volume = 28 | issue = 10 | pages = 1726–35; discussion 1710–1 | date = October 2006 | pmid = 17157129 | doi = 10.1016/j.clinthera.2006.10.010 }} A study of employer-related health costs from a Fortune 100 company conducted with data from the 1990s found people with IBS incurred US$4527 in claims costs vs. $3276 for controls.{{cite journal | vauthors = Leong SA, Barghout V, Birnbaum HG, Thibeault CE, Ben-Hamadi R, Frech F, Ofman JJ | title = The economic consequences of irritable bowel syndrome: a US employer perspective | journal = Archives of Internal Medicine | volume = 163 | issue = 8 | pages = 929–35 | date = April 2003 | pmid = 12719202 | doi = 10.1001/archinte.163.8.929 | doi-access = free }} A study on Medicaid costs conducted in 2003 by the University of Georgia College of Pharmacy and Novartis found IBS was associated in an increase of $962 in Medicaid costs in California, and $2191 in North Carolina. People with IBS had higher costs for physician visits, outpatients visits, and prescription drugs. The study suggested the costs associated with IBS were comparable to those found for people with asthma.{{cite journal | vauthors = Martin BC, Ganguly R, Pannicker S, Frech F, Barghout V | s2cid = 19353148 | title = Utilization patterns and net direct medical cost to Medicaid of irritable bowel syndrome | journal = Current Medical Research and Opinion | volume = 19 | issue = 8 | pages = 771–80 | year = 2003 | pmid = 14687449 | doi = 10.1185/030079903125002540 | url = http://www.medscape.com/viewarticle/465472 | archive-url = https://web.archive.org/web/20031220161925/http://www.medscape.com/viewarticle/465472 | df = mdy-all | url-status = live | archive-date = December 20, 2003 }}

Individuals with IBS have been found to have decreased diversity and numbers of Bacteroidota microbiota. Preliminary research into the effectiveness of fecal microbiota transplant in the treatment of IBS has been very favourable with a 'cure' rate of between 36 percent and 60 percent with remission of core IBS symptoms persisting at 9 and 19 months follow up.{{cite journal | vauthors = Aroniadis OC, Brandt LJ | s2cid = 39943619 | title = Fecal microbiota transplantation: past, present and future | journal = Current Opinion in Gastroenterology | volume = 29 | issue = 1 | pages = 79–84 | date = January 2013 | pmid = 23041678 | doi = 10.1097/MOG.0b013e32835a4b3e | doi-access = free }}{{cite journal | vauthors = Smits LP, Bouter KE, de Vos WM, Borody TJ, Nieuwdorp M | title = Therapeutic potential of fecal microbiota transplantation | journal = Gastroenterology | volume = 145 | issue = 5 | pages = 946–53 | date = November 2013 | pmid = 24018052 | doi = 10.1053/j.gastro.2013.08.058 }} Treatment with probiotic strains of bacteria has shown to be effective, though not all strains of microorganisms confer the same benefit and adverse side effects have been documented in a minority of cases.{{cite journal | vauthors = Ford AC, Quigley EM, Lacy BE, Lembo AJ, Saito YA, Schiller LR, Soffer EE, Spiegel BM, Moayyedi P | s2cid = 205100508 | title = Efficacy of prebiotics, probiotics, and synbiotics in irritable bowel syndrome and chronic idiopathic constipation: systematic review and meta-analysis | journal = The American Journal of Gastroenterology | volume = 109 | issue = 10 | pages = 1547–61; quiz 1546, 1562 | date = October 2014 | pmid = 25070051 | doi = 10.1038/ajg.2014.202 }}

There is increasing evidence for the effectiveness of mesalazine (5-aminosalicylic acid) in the treatment of IBS.{{cite journal | vauthors = Klotz U | title = The pharmacological profile and clinical use of mesalazine (5-aminosalicylic acid) | journal = Arzneimittel-Forschung | volume = 62 | issue = 2 | pages = 53–8 | date = February 2012 | pmid = 22344548 | doi = 10.1055/s-0031-1299685 | s2cid = 11264827 }} Mesalazine is a drug with anti-inflammatory properties that has been reported to significantly reduce immune mediated inflammation in the gut of IBS affected individuals with mesalazine therapy resulting in improved IBS symptoms as well as feelings of general wellness in IBS affected people. It has also been observed that mesalazine therapy helps to normalise the gut flora which is often abnormal in people who have IBS. The therapeutic benefits of mesalazine may be the result of improvements to the epithelial barrier function.{{cite journal | vauthors = Barbara G, Stanghellini V, Cremon C, De Giorgio R, Fronzoni L, Serra M, Corinaldesi R | s2cid = 5184633 | title = Aminosalicylates and other anti-inflammatory compounds for irritable bowel syndrome | journal = Digestive Diseases | volume = 27 | issue = Suppl 1 | pages = 115–21 | year = 2009 | pmid = 20203507 | doi = 10.1159/000268131 }} Treatment based on "abnormally" high IgG antibodies cannot be recommended.{{cite journal | vauthors = Philpott H, Nandurkar S, Lubel J, Gibson PR | title = Alternative investigations for irritable bowel syndrome | journal = Journal of Gastroenterology and Hepatology | volume = 28 | issue = 1 | pages = 73–7 | date = January 2013 | pmid = 23033865 | doi = 10.1111/j.1440-1746.2012.07291.x | s2cid = 1877012 }}

Differences in visceral sensitivity and intestinal physiology have been noted in IBS. Mucosal barrier reinforcement in response to oral 5-HTP was absent in IBS compared to controls.{{cite journal | vauthors = Keszthelyi D, Troost FJ, Jonkers DM, van Eijk HM, Lindsey PJ, Dekker J, Buurman WA, Masclee AA | title = Serotonergic reinforcement of intestinal barrier function is impaired in irritable bowel syndrome | journal = Alimentary Pharmacology & Therapeutics | volume = 40 | issue = 4 | pages = 392–402 | date = August 2014 | pmid = 24943480 | doi = 10.1111/apt.12842 | s2cid = 43740780 | doi-access = free }} IBS/IBD individuals are less often HLA DQ2/8 positive than in upper functional gastrointestinal disease and healthy populations.{{cite journal | vauthors = DiGiacomo D, Santonicola A, Zingone F, Troncone E, Caria MC, Borgheresi P, Parrilli G, Ciacci C | title = Human leukocyte antigen DQ2/8 prevalence in non-celiac patients with gastrointestinal diseases | journal = World Journal of Gastroenterology | volume = 19 | issue = 16 | pages = 2507–13 | date = April 2013 | pmid = 23674852 | pmc = 3646141 | doi = 10.3748/wjg.v19.i16.2507 | doi-access = free }}

Efficacy of mast cell directed therapies in irritable bowel syndrome is an area of ongoing research.{{cite journal |vauthors=Coppens D, Kips M, Stiévenard T, Mertens C, De Schepper H |title=Efficacy of mast cell directed therapies in irritable bowel syndrome: a systematic review |journal=Acta Gastroenterol Belg |volume=87 |issue=1 |pages=15–27 |date=2024 |pmid=38431786 |doi=10.51821/87.1.12487}}

A similar syndrome is found in rats (Rattus spp.). In rats a short-chain fatty acid receptor is involved, a free fatty acid receptor 2 subtype {{endash}} {{ Visible anchor | GPR43 }} {{endash}} that is expressed in both enteroendocrine cells and mucosal mast cells. These cells then respond in an exaggerated way to the IBS rat's own large quantity of maldigestion products.

{{cite journal | vauthors = Camilleri M | title = Peripheral mechanisms in irritable bowel syndrome | journal = The New England Journal of Medicine | volume = 367 | issue = 17 | pages = 1626–1635 | date = October 2012 | pmid = 23094724 | doi = 10.1056/nejmra1207068 }}

• Mucorrhea

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{{Commons category}}

{{Medical condition classification and resources

| DiseasesDB = 30638

| ICD10 = {{ICD10|K|58||k|55}}

| ICD9 = {{ICD9|564.1}}

| ICDO =

| OMIM =

| MedlinePlus = 000246

| eMedicineSubj = med

| eMedicineTopic = 1190

| MeshID = D043183

}}

{{Irritable bowel syndrome}}

{{Gastroenterology}}

{{Authority control}}

{{DEFAULTSORT:Irritable Bowel Syndrome}}

Category:Abdominal pain

Category:Chronic pain syndromes

Category:Conditions diagnosed by stool test

Category:Diseases of intestines

Category:Gastrointestinal motility disorders

Category:Syndromes affecting the gastrointestinal tract

Category:Syndromes of unknown causes

Category:Wikipedia medicine articles ready to translate

Category:Wikipedia neurology articles ready to translate