Melatonin

Melatonin is one of the most-widely-used over-the-counter sleep supplements globally, with a research base spanning sleep onset latency, jet lag adjustment, shift-work sleep disorder, delayed sleep phase disorder, age-related sleep changes, and circadian rhythm disorders in blind individuals and certain neurodevelopmental conditions. The endogenous hormone is produced by the pineal gland in response to darkness, peaking in the middle of the biological night. Supplemental melatonin acts on MT1 and MT2 receptors in the brain to mimic the dark-signal and shift the circadian phase, which is mechanistically distinct from sedative-style sleep medications.

The outcome dimensions covered most heavily are sleep onset latency (the most-studied effect, examined across many trial designs and populations), jet lag prevention and treatment, shift-work sleep, age-related sleep changes (where endogenous melatonin production has declined), and circadian rhythm disorders in specific populations. Newer research streams include melatonin in autism spectrum disorder, anxiety contexts, and antioxidant/anti-inflammatory effects at much higher doses than sleep applications. The supplement-vs-physiological dose mismatch is a recurring topic in the literature: most consumer supplements provide 1-10 mg, while physiologically-relevant trials have used 0.1-0.3 mg, with research examining whether higher doses provide additional benefit for sleep timing.

Demographically, the literature is unusually broad across ages: pediatric populations feature heavily in delayed sleep phase and autism-related sleep research; older adults feature in age-related sleep decline studies; healthy adults dominate jet-lag and shift-work research. Sustained-release vs. immediate-release formulations is an active area, with immediate-release favored for sleep onset and sustained-release favored for sleep maintenance. Timing of administration is studied alongside dose: trials range from 30 minutes to about 3 hours before desired sleep onset.

Melatonin has an unusually clean short-term safety profile and is sold over-the-counter in the United States and many other countries (it is prescription-only in some European countries and the UK). The most-common short-term adverse events at typical supplement doses are mild and transient: morning grogginess, headache, vivid dreams, and mood changes. Long-term safety data are limited; no established tolerable upper limit exists. Drug interactions to note include sedatives and CNS depressants (additive effects), anticoagulants (theoretical interaction with platelet function), and antihypertensives (blood pressure rose in one trial in people taking a calcium channel blocker). Pregnancy and breastfeeding safety is not well-established. People taking the above medications, those with epilepsy or autoimmune conditions, and those pregnant or breastfeeding should consult a clinician before use.

This summary is informational and not medical advice. Consult a clinician before starting or changing any supplement, especially if you take prescription medications.