Sleep-inducing effects of exogenous melatonin administration.

In this report current data is reviewed indicating that melatonin, the main hormone secreted by the pineal gland at night, participates in sleep regulation in humans. Evidence supporting this role relies on findings that abnormal melatonin secretion, induced by a variety of commonly used drugs, and in clinical disorders of the nervous system, are associated with sleep disturbances, and that melatonin has beneficial sleep-inducing effects in elderly melatonin-deficient insomniacs, and in children with sleep disorders. The time of melatonin administration, rather than the pharmacological dose, is a crucial factor regarding its potency as a sleep-inducing agent. Possible operating mechanisms explaining melatonin hypnotic effects are discussed.