Acute effects of low doses of melatonin on the sleep of young healthy subjects

This study was undertaken to evaluate the acute effects of single low doses of melatonin given to healthy volunteers in the evening, Six healthy male volunteers (age range 22-24 years) participated in this study, after signin g an informed consent form. They received in a double-blind fashion placebo or 0.3 or 1.0 mg melatonin at three fixed times: 18:00, 20:00, and 21:00 h r. Polysomnographic recordings began immediately thereafter, with their bei ng allowed to sleep, Prior to each experimental session and in the followin g morning, subjects completed a sleep quality questionnaire, the Profile of Mood States, the Stanford Sleepiness Scale, and underwent a visual reactio n test. Significant decrease on sleep latencies was found following melaton in treatment at 18:00 and 20:00 hr. In addition, melatonin tended to improv e sleep efficiency and to reduce intermittent wakefulness. However, at 21:0 0 hr. 0.3 mg melatonin increased latency to sleep onset and 1.0 mg melatoni n had no effect on sleep variables. Furthermore, melatonin given at differe nt times did not alter subjective sleepiness, mood, and reaction time in th e following morning. The results from the present study support the notion that administration of low doses of melatonin, mimicking the nocturnal phys iological concentration of this hormone may exert immediate sleep-inducing effects.