Fig. (4).

Summary of the results reported in studies evaluating the sleep-inducing and the sleep-promoting effect of exogenous melatonin in healthy subjects. Studies are organized as a function of the timing of administration (morning, afternoon, early evening, night). MEL+ refers to sleep episodes scheduled when endogenous melatonin levels were elevated, while MEL- refers to sleep episodes scheduled when endogenous melatonin levels were low to absent. Sleepiness refers to the acute effects of exo-MEL. Abbreviations: S: sleepiness; F: fatigue, SOL, sleep onset latency; TST, total sleep time; WASO, waking after sleep onset; SE, sleep efficiency; REM, rapid eye movements sleep; S1, Stage 1; S2, Stage 2; S3, Stage 3; S4, Stage 4, SWS, slow wave sleep; AW: awakenings; ss: sleep spindles; SOT: sleep onset time; SQ: sleep quality. Cells in blue indicate that exogenous melatonin had a significant effect on the evaluated variable, cells in red indicate the absence of melatonin-induced effect on the evaluated variable.