Administration of melatonin at bedtime for 2 weeks significantly increased rectal pain threshold and attenuated abdominal pain in patients with irritable bowel syndrome and sleep disturbance, according to a randomized, double-blind, placebo-controlled study conducted in Singapore.
G.H. Song of the National University of Singapore and colleagues reported that 40 patients with IBS took 3 mg of melatonin or placebo nightly and completed questionnaires on psychological, sleep, and bowel symptoms. Patients also underwent overnight polysomnography and rectal manometry.
The improvements in abdominal pain were realized without changes in sleep disturbance or psychological distress. The treatment did not significantly change the frequency of defecation or stool type; nor did it change rectal pressures during squeezing, pushing, or resting states (Gut 2005;54:1402–7).
In a commentary, Sigrid Elsenbruch, Ph.D., of the University Clinic of Essen, Germany, noted that the Singapore researchers did not screen their patients for mood disorders, which can be associated with alterations in sleep physiology, but concluded that the findings “are intriguing and call for replication and further study” (Gut 2005;54:1353–4).