EFFECTS OF LOW ORAL DOSES OF MELATONIN, GIVEN 2-4 HOURS BEFORE HABITUAL BEDTIME, ON SLEEP IN NORMAL YOUNG HUMANS

Low oral doses of melatonin raise serum melatonin concentrations to th ose normally occurring nocturnally and facilitate polysomnographically assessed sleep onset when given at different time points throughout t he day, without altering mood or performance on the morning following treatment. In the present study, 12 young healthy volunteers, free of sleep disturbances, received 0.3 or 1.0 mg of melatonin or placebo at 2100 hours, 2-4 hours prior to their habitual bedtime. Polysomnographi c recording of overnight sleep began at 2200 hours and continued until 0700 hours the following morning, when subjects were awakened. Sleep onset latency and latency to stage 2 sleep were significantly decrease d as a result of melatonin treatment. Neither dose of melatonin signif icantly altered sleep architecture. Administration of the lower dose o f melatonin (0.3 mg) at 2100 hours elevated serum melatonin to levels within the normal nocturnal range (113 +/- 13.5 pg/ml) at the time the sleep test was initiated. Neither melatonin dose caused ''hangover ef fects'', as assessed by self-reports or by mood and performance tests administered on the morning following treatment. These observations pr ovide additional evidence that nocturnal melatonin secretion has a sle ep-promoting function. They also indicate that an increase in serum me latonin concentrations, within the normal physiologic range, does not significantly alter sleep architecture in subjects with normal sleep w ho receive the treatment several hours prior to their habitual bedtime .