In North America melatonin is a popular wonder drug which has the legal status of a “nutritional supplement,” although that is a legal fiction. As a result it is not regulated as a medicine and is advertised and sold widely—in pharmacies, drug stores, health food shops, and on the internet. Many millions of people use it, mostly because they believe it will help them sleep. However, the claims made for melatonin products and their pharmaceutical quality are not controlled, and their safety has not been systematically studied.

The systematic review in this issue by Buscemi and colleagues at the University of Alberta (p 385) examines the value of melatonin in sleep disorders.1 Such a review is much needed, as the support for this work from the US National Center for Complementary and Alternative Medicine recognises.

A thorough search of the literature yielded 12 mostly small randomised controlled trials of melatonin in secondary sleep disorders associated with medical and neurological disorders and those related to substance misuse. Another set of 13 randomised …