A common pattern: you can't sleep, you take melatonin, it doesn't work, you take more. The trial data points to a different model. Melatonin is better at moving your clock than at knocking you out.
As a sleep aid: small effects
A meta-analysis of 19 randomized trials with 1,683 people with primary sleep disorders found melatonin:
- shortened the time to fall asleep by about 7 minutes;
- lengthened total sleep by about 8 minutes;
- modestly improved overall sleep quality.
The effects were modest but did not fade with continued use. Longer trials and higher doses showed somewhat bigger effects on sleep onset and total sleep.
As a clock-shifter: clearer effects
In delayed sleep phase disorder, where people's internal clock runs late, a meta-analysis of 5 trials in 91 adults and 4 trials in 226 children found melatonin:
- moved the body's own melatonin onset earlier by about 1.2 hours;
- moved the clock time of falling asleep earlier by about 40 minutes;
- shortened time to fall asleep by about 23 minutes.
Wake-up time and total sleep time did not change significantly. A Cochrane review of jet lag found clear benefit when crossing five or more time zones, with doses from 0.5 to 5 mg working similarly.
Timing beats dose
A phase-response study compared 0.5 mg with 3 mg taken daily for three days. The biggest advances came when 0.5 mg was taken in the afternoon, 2 to 4 hours before the body's own evening melatonin rise. The optimal time was later for the lower dose, and when each dose was given at its own best time, both moved the clock by a similar amount.
So "it didn't work, take more" is often the wrong fix. The variable with more leverage is when.
What it does not answer
The headline outcomes in these trials are sleep onset, total sleep and clock timing. If your problem is waking at 3 a.m. and lying awake, these numbers do not speak to it directly. See our post on night waking.
The label problem
A lab analysis of 31 melatonin products found actual content ranging from 83% below to 478% above the label, and serotonin in some products. "1 mg" on the bottle may not be 1 mg. Higher doses (10 mg and up) did not increase serious adverse events in a safety meta-analysis, but did bring more drowsiness, headache and dizziness.
Sources
- Ferracioli-Oda E, Qawasmi A, Bloch MH. 2013. Meta-analysis: melatonin for the treatment of primary sleep disorders. PLoS One. PubMed 23691095
- van Geijlswijk IM, Korzilius HP, Smits MG. 2010. The use of exogenous melatonin in delayed sleep phase disorder: a meta-analysis. Sleep. PubMed 21120122
- Burgess HJ et al. 2010. Human phase response curves to three days of daily melatonin: 0.5 mg versus 3.0 mg. J Clin Endocrinol Metab. PubMed 20410229
- Herxheimer A, Petrie KJ. 2002. Melatonin for the prevention and treatment of jet lag. Cochrane Database Syst Rev. PubMed 12076414
- Erland LA, Saxena PK. 2017. Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content. J Clin Sleep Med. PubMed 27855744
- Menczel Schrire Z et al. 2022. Safety of higher doses of melatonin in adults: A systematic review and meta-analysis. J Pineal Res. PubMed 34923676
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