Melatonin

Research summary

• Melatonin is among the most heavily meta-analyzed sleep supplements, and the picture that emerges is a real but modest effect that varies by population.
• Multiple independent meta-analyses of randomized, placebo-controlled trials find melatonin significantly shortens sleep onset latency (weighted mean differences of roughly 5-12 minutes across analyses) and modestly increases total sleep time, with a 2024 dose-response meta-analysis finding effects peak around 4 mg/day and improve when dosing is timed closer to the target sleep episode.
• Evidence is more mixed than commonly assumed for its core marketed use: a 2022 meta-analysis restricted to chronic insomnia found melatonin was not significantly effective in adults without comorbidities, though it was effective in children and adolescents and in adults with comorbid insomnia.
• Effects are better established for circadian-timing problems — delayed sleep phase disorder and neurodevelopmental-disorder-related sleep problems in children — and for jet lag, per a systematic review evaluating melatonin among other interventions.
• Prolonged-release melatonin shows a small-to-medium effect on sleep onset latency in general and a notably larger effect on sleep efficiency in adults over 55.
• Safety data across roughly 3,900 participants in higher-dose trials (≥10 mg) found no clear excess of serious adverse events, though most underlying studies carried meaningful risk of bias.
• Net: melatonin works, but modestly, and is more reliably useful for circadian misalignment than as a general adult insomnia cure.