The hypnotic effects of melatonin treatment on diurnal sleep in humans.

This study investigated the hypnotic effects of 10 mg melatonin and placebo, which were administered at 10.00 h, according to a single-blind crossover design, on an 8-h diurnal sleep from 11.00 to 19.00 h, following a full night of sleep. The subjects were six healthy male students, each of whom underwent polysomnography and rectal temperature monitoring. Melatonin treatment significantly increased total sleep time in diurnal sleep (403.2+/-SD 72.8 min and 258.5+/-118.3 min, P<0.001). As to changes in rectal temperature during diurnal sleep, however, there were no significant differences between the melatonin and placebo conditions. Thus, these results indicated that melatonin administered at 10.00 h had direct hypnotic effects on diurnal sleep.