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

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.