OBJECTIVE: Psychiatric morbidity is high among patients who present to referral centers with irritable bowel syndrome (IBS). However, few studies have investigated the relationship between psychiatric disturbance and IBS in community samples. We hypothesized that psychiatric disorders are linked to IBS in the general community, but this is influenced by the criteria used to establish a diagnosis of IBS. METHODS: The data were collected from a birth cohort born in Dunedin (New Zealand) between April 1972 and March 1973. This cohort consisted of 1037 members (52% male), who were assessed at ages 3, 5, 7, 9, 11, 13, 15, 18, 21, and 26 yr. GI symptoms were recorded at age 26 yr, using an abbreviated version of the Bowel Symptom Questionnaire; psychiatric history was obtained at ages 18 and 21 yr, using a modified version of the Diagnostic Interview Schedule. RESULTS: The prevalence of IBS was 12.7% according to the Manning criteria and 4.3% according to the Rome II criteria. The lBS was not significantly related to a diagnostic history for psychiatric illness overall, nor to a history of anxiety disorders, depressive disorders, and substance dependence. These results were independent of the IBS criteria used; there was no association between psychiatric history and IBS when IBS was defined according to the Manning criteria (p = 0.11 to 0.98) or the Rome criteria (p = 0.18 to 0.92); Rome and Manning criteria subjects did not significantly differ from each other in terms of psychiatric history (p = 0.16 to 0.89). CONCLUSION: In a cohort of young adults with IBS from New Zealand, lBS appears to not be related to psychiatric disorders.