Melatonin: therapeutic use in sleep disorders

To review the use of melatonin in sleep disorders, including jet lag, shift work disorder, insomnia, and sleep cycle disorders in neurologically impaired patients.

A MEDLINE search (1966 to April 1996) was performed that included clinical studies and reviews on melatonin in the English language. References used in those articles were also screened for additional information.

All published trials were considered for inclusion in this review, with an emphasis placed on more recently published studies (last 5 years).

There is significant evidence that links the hormone melatonin to circadian sleep cycles in humans. It has been suggested that in situations where the endogenous melatonin concentration is reduced (advancing age) or the normal circadian cycle is disrupted (jet lag, shift work, blind patients), supplementation with exogenous melatonin may improve both sleep duration and quality. Limited data from generally short-term trials and anecdotal reports suggest that melatonin may be effective in several of these sleep disorders. Melatonin use in jet lag appears to decrease jet lag symptoms and hasten the return to normal energy levels. Melatonin may be helpful in rotating shift schedules to improve sleep quality and maintain normal circadian rhythm. In some patients with insomnia, melatonin appears to induce sleep onset. The optimal dosage and timing of drug administration is still unclear.

Although there is some evidence that melatonin may have modest efficacy, especially in insomnia, jet lag, and sleep disorders in neurologically impaired patients, adequate long-term studies examining both efficacy and toxicity are lacking. In addition, further studies evaluating dose-response relationships and drug interactions are warranted.