# What are the benefits and harms of melatonin for insomnia in adults?

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**Summary:** A small reduction in sleep latency and modest gain in sleep time; CBT-I is first-line, melatonin only weakly recommended.

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].

## Limitations

- 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.

## Sources

1. [III / Systematic review] Meta-Analysis: Melatonin for the Treatment of Primary Sleep Disorders. PLoS ONE (2013). PMID 23691095. https://pubmed.ncbi.nlm.nih.gov/23691095/
2. [I / Guideline] The European Insomnia Guideline: an update on the diagnosis and treatment of insomnia 2023. Journal of Sleep Research (2023). DOI 10.1111/jsr.14035. https://onlinelibrary.wiley.com/doi/10.1111/jsr.14035

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