OBJECTIVE: Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder. Evidence for treatment of the condition with antidepressants and psychological therapies is conflicting. DESIGN: Systematic review and meta-analysis of randomised controlled trials (RCTs). MEDLINE, EMBASE and the Cochrane Controlled Trials Register were searched (up to May 2008). SETTING: RCTs based in primary, secondary and tertiary care. PATIENTS: Adults with IBS. INTERVENTIONS: Antidepressants versus placebo, and psychological therapies versus control therapy or "usual management". MAIN OUTCOME MEASURES: Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% confidence interval (CI). The number needed to treat (NNT) was calculated from the reciprocal of the risk difference. RESULTS: The search strategy identified 571 citations. Thirty-two RCTs were eligible for inclusion: 19 compared psychological therapies with control therapy or "usual management", 12 compared antidepressants with placebo, and one compared both psychological therapy and antidepressants with placebo. Study quality was generally good for antidepressant but poor for psychological therapy trials. The RR of IBS symptoms persisting with antidepressants versus placebo was 0.66 (95% CI, 0.57 to 0.78), with similar treatment effects for both tricyclic antidepressants and selective serotonin reuptake inhibitors. The RR of symptoms persisting with psychological therapies was 0.67 (95% CI, 0.57 to 0.79). The NNT was 4 for both interventions. CONCLUSIONS: Antidepressants are effective in the treatment of IBS. There is less high-quality evidence for routine use of psychological therapies in IBS, but available data suggest these may be of comparable efficacy.