What are the benefits and harms of melatonin for insomnia in adults?
In adults with primary sleep disorders, melatonin produces a small reduction in the time taken to fall asleep and a modest increase in total sleep time versus placebo. A meta-analysis of 19 randomised studies found sleep-onset latency reduced by roughly 7 minutes and total sleep time increased by about 8 minutes, with improved sleep quality [1]. The effect size is small and its clinical importance is debated.
The 2023 European insomnia guideline recommends cognitive behavioural therapy for insomnia (CBT-I) as first-line treatment and gives only a weak recommendation for prolonged-release melatonin, mainly in adults aged 55 and over, reflecting limited efficacy [2].
Melatonin is generally well tolerated over short-term use, with headache, daytime drowsiness, and dizziness the most common effects; long-term safety data are limited, and unregulated over-the-counter products vary widely in actual content [1, 2].
- Average benefits are small and may not be clinically meaningful for many patients; trial populations and melatonin formulations/doses were heterogeneous.
- Long-term efficacy and safety beyond a few months are poorly characterised.
Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders
The European Insomnia Guideline: an update on the diagnosis and treatment of insomnia 2023
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