Evidence Level
Melatonin is one of the most extensively studied sleep supplements. Ferracioli-Oda et al. (2013) conducted a meta-analysis of 19 randomized controlled trials (RCTs) involving 1,683 subjects, demonstrating that melatonin significantly reduces sleep onset latency by -7.06 minutes on average, increases total sleep time by +8.25 minutes, and improves overall sleep quality. Herxheimer & Petrie (2002) confirmed melatonin's efficacy for jet lag prevention and treatment through a Cochrane review of 10 trials. Brzezinski et al. (2005) meta-analyzed 17 studies, confirming melatonin's sleep-promoting effects and noting that its efficacy does not diminish with continued use over weeks.
A key finding across the literature is the absence of a clear dose-response relationship. Zhdanova et al. (2001) demonstrated that physiological doses (0.3mg) were as effective as pharmacological doses (3mg) for improving sleep in older adults with insomnia. Recent studies have expanded on melatonin's applications, including its use in critically ill patients. Tang et al. (2025) found that melatonin may reduce delirium, slightly shorten ICU stay, and improve sleep quality in this population, though evidence is of low certainty.
In heart failure patients, Daliri et al. (2025) reported that melatonin improves quality of life (p=0.001), though it has no significant effect on ejection fraction (p=0.27). Additionally, Cruz-Sanabria et al. (2024) systematically reviewed 26 RCTs to optimize the timing and dosage of melatonin as a sleep-promoting drug, further supporting its efficacy across diverse populations.