Melatonin improves bowel symptoms in female patients with irritable bowel syndrome: a double‐blind placebo‐controlled study

Summary Background : Melatonin is involved in the regulation of gastrointestinal motility and sensation. Aim : To determine the potential therapeutic effects of melatonin in irritable bowel syndrome (IBS). Method : Seventeen female patients satisfying the Rome II criteria for IBS were randomized to receive either melatonin 3 mg nocte or identically appearing placebo 1 nocte for 8 weeks, followed by a 4‐week washout period and placebo or melatonin in the reverse order for another 8 weeks. Three validated questionnaires – the GI symptom, the sleep questionnaires and the Hospital Anxiety and Depression Scale – were used to assess symptom severity and to compute the IBS, sleep and anxiety/depression scores, respectively. Results : Improvements in mean IBS scores were significantly greater after treatment with melatonin (3.9 ± 2.6) than with placebo (1.3 ± 4.0, P = 0.037). Percent response rate, defined as percentage of subjects achieving mild‐to‐excellent improvement in IBS symptoms, was also greater in the melatonin‐treated arm (88% vs. 47%, P = 0.04). The changes in mean sleep, anxiety, and depression scores were similar with either melatonin or placebo treatment. Conclusions : Melatonin is a promising therapeutic agent for IBS. Its therapeutic effect is independent of its effects on sleep, anxiety or depression.