Evidence Level
Melatonin is one of the most extensively studied sleep supplements. Ferracioli-Oda et al. (2013) published a pivotal meta-analysis of 19 RCTs involving 1,683 subjects, demonstrating that melatonin significantly reduces sleep onset latency (weighted mean difference -7.06 min), increases total sleep time (+8.25 min), and improves overall sleep quality. Herxheimer & Petrie (2002) conducted a Cochrane review of 10 trials confirming melatonin's efficacy for jet lag prevention and treatment. Brzezinski et al. (2005) meta-analyzed 17 studies confirming melatonin's sleep-promoting effects and noted that efficacy did 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.