EFFECT OF PHARMACOLOGICAL DAYTIME DOSES OF MELATONIN ON HUMAN MOOD AND PERFORMANCE

Melatonin (10, 20, 40, or 80 mg, PO) or placebo was administered at 11 45 hours on five separate occasions to 20 healthy male volunteers and the effects on serum melatonin levels, mood, performance, and oral tem perature were monitored. Subjects were studied between 0930 and 1700 h ours. A battery of interactive computer tasks designed to assess perfo rmance and mood was completed, oral temperature was measured, and bloo d samples were taken for serum melatonin radioimmunoassay. The areas u nder the time-melatonin concentration curve (AUC) varied significantly in proportion to the various melatonin doses. Compared with placebo t reatment, all melatonin doses significantly decreased oral temperature , number of correct responses in auditory vigilance, response latency in reaction time, and self-reported vigor. Melatonin also increased se lf-reported fatigue, confusion, and sleepiness.