Song GH et al. (2005) Melatonin improves abdominal pain in irritable bowel syndrome patients who have sleep disturbances: a randomised, double-blind, placebo controlled study. Gut 54: 1402–1407

Sleep disturbance is highly prevalent in irritable bowel syndrome (IBS) patients. As melatonin has been associated with both sleep promotion and the regulation of gastro-intestinal motility, Song and colleagues carried out a randomized, placebo-controlled study to assess its efficacy in treating symptoms of IBS and sleep disturbance.

In total, 40 patients with IBS and sleep disturbance were randomized 1:1 to receive either 14 days treatment with melatonin 3 mg daily at bedtime, or placebo. Bowel symptoms, sleep disturbance and the psychological status of participants were recorded at baseline and after completion of 14 days of therapy, by means of questionnaires: rectal manometry and overnight polysomnography were also performed at these two evaluation points.

After 2 weeks, patients receiving melatonin had a significantly greater decrease in abdominal pain and significantly increased sensory thresholds for urgency and pain, compared with those receiving placebo. The quality and quantity of patients' sleep, however, did not differ significantly between the two groups. In addition, there was no significant difference in the anxiety and depression scores of patients receiving melatonin compared with placebo.

The authors conclude that melatonin is effective in reducing abdominal pain and enhancing rectal pain thresholds in IBS patients, but this effect is independent of its effect on sleep and psychological parameters.