Efficacy of melatonin as a sleep-promoting agent.

Numerous studies have demonstrated sleep-promoting effects of melatonin treatment in humans, as evidenced by subjects' self-reports, polysomnographic recordings, and continuous actigraphic registration of motor activity. The sleep-promoting effects of either physiological or pharmacological doses of melatonin typically are observed within 1 h following treatment regardless of the time of melatonin administration. This fact indicates the acute nature of this effect of melatonin on sleep, independent of any effect of the melatonin treatment on circadian organization. This article considers a dose dependency of melatonin effects on sleep, interindividual variability, and age-related differences in circulating melatonin levels produced in response to a given dose of the hormone. Possible side effects of melatonin treatment, and the use of an animal model to serve as a guide in the development of therapeutic applications, also are considered.