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Nootropics

Melatonin

A circadian-timing hormone useful for jet lag and selected sleep-timing problems, with only small average effects in chronic insomnia.

Moderate
Evidence rating
Evidence review

What the evidence says

Melatonin is a hormone that signals biological night, so timing can matter more than taking a large sedative dose. Evidence is most coherent for shifting circadian timing and reducing jet-lag symptoms when it is taken at an appropriate destination bedtime.[1][2]

For primary sleep disorders, a meta-analysis found small average improvements in sleep onset, total sleep time, and sleep quality rather than a dramatic hypnotic effect. Because trials and products vary, the American Academy of Sleep Medicine issued a weak recommendation against melatonin for routine treatment of chronic insomnia in adults.[3][4]

More is not necessarily better: dose and clock time change the biological effect, extended-release products behave differently from immediate-release products, and morning grogginess can erase a small nighttime gain. Behavioral treatment such as CBT-I remains the best-supported first-line approach for chronic insomnia.[4][1]

Supplement quality is a major limitation. Laboratory testing of 31 products found melatonin content ranging from 83% below to 478% above the label and detected serotonin in 26%. Short-term use commonly causes headache, dizziness, nausea, or sleepiness; long-term safety, pregnancy, and many drug interactions remain insufficiently defined.[5][6][1]

Potential benefits

  • Can reduce jet-lag symptoms when timed appropriately around destination bedtime.[2]
  • May modestly shorten sleep onset and slightly increase total sleep in some sleep disorders.[3]

Side effects and cautions

  • May cause daytime sleepiness, headache, dizziness, nausea, or vivid dreams.[1][6]
  • Retail products may contain far more or less melatonin than labeled and occasionally undeclared serotonin.[5]
How we scored it

Evidence breakdown

Controlled trials support circadian uses and modest sleep-onset effects, while chronic-insomnia guidance is cautious and supplement content is often unreliable.

Clinical relevanceHigh

Trials assess sleep onset, total sleep, daytime consequences, and jet-lag symptoms.

Study qualityModerate

Numerous controlled trials exist, but dose, timing, formulation, age, and diagnosis vary.

Safety dataModerate

Short-term adverse effects are usually mild; long-term use and supplement quality remain uncertain.

References

Full source list

  1. Melatonin: What You Need To Know

    National Center for Complementary and Integrative Health · 2025

  2. Melatonin for the prevention and treatment of jet lag

    Cochrane Database of Systematic Reviews · 2002

  3. Meta-analysis: melatonin for the treatment of primary sleep disorders

    PLoS One · 2013

  4. Clinical Practice Guideline for the Pharmacologic Treatment of Chronic Insomnia in Adults

    Journal of Clinical Sleep Medicine · 2017

  5. Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content

    Journal of Clinical Sleep Medicine · 2017

  6. Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review

    CNS Drugs · 2019