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Melatonin: what the evidence actually shows

settled  melatonin — established for sleep onset; dosing myths persist

Reviewed by Substrate editorial, Independent research collective ·

⚠ Safety in context

Evidence by outcome

sleepgrade Bmoderate certainty— reduces time to fall asleep; best for circadian timing
cognitiongrade Bmoderate certainty— Meta-analysis of RCTs in older adults with cognitive impairment: melatonin produced a modest improvement in cognition (MMSE +1.8 points) and total sleep time (+12.4 minutes), with a small reduction in neuropsychiatric symptoms. The authors conclude effects approach — but fall short of — definitive clinical efficacy, with substantial heterogeneity between trials.
stressgrade Bmoderate certainty— Cochrane review of 27 RCTs (2319 participants): melatonin reduced preoperative anxiety versus placebo, with effects broadly comparable to benzodiazepines such as midazolam in the trials that compared them. Evidence for postoperative anxiety was less certain. This is an acute, perioperative-anxiety context, not general everyday stress.
inflammationgrade Bmoderate certainty— Meta-analysis of 31 clinical trials (1517 participants): melatonin significantly reduced inflammatory markers IL-1, IL-6, IL-8, and TNF versus placebo, but had no significant effect on C-reactive protein (CRP). After correcting for publication bias, effects on IL-1, IL-6, and IL-8 remained significant — a real anti-inflammatory signal on cytokines specifically, not on CRP.
migraine frequencygrade Clow certainty— Systematic review: melatonin showed promise for migraine prophylaxis, reducing attack frequency in several trials, with a tolerability profile comparable to or better than some standard preventives. The evidence base is small and heterogeneous.
moodgrade Clow certainty— Systematic review: melatonin has been studied as a treatment for mood disorders, with some signal in specific contexts (e.g. seasonal or circadian-related), but overall evidence for a mood benefit is limited and inconsistent.
blood sugargrade Clow certainty— Meta-analysis of 12 RCTs: melatonin supplementation significantly reduced fasting glucose and improved insulin sensitivity (QUICKI index), but had no significant effect on insulin levels, HOMA-IR, or HbA1c. A partial biomarker signal on fasting glucose specifically, not comprehensive glycemic control.

People say · Evidence shows

“Taking more melatonin makes sleep deeper”

aheadlargemechanistic speculation

Grade history

Re-review cadence: every 12 months (Grade A/B) · next scheduled by · methodology v1.

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sources: PMID:23691095 · PMID:15649737 · PMID:41240058 · PMID:33319916 · PMID:33581247 · PMID:30653130 · PMID:28612993 · PMID:30396207

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Plain-text citation
Substrate. Melatonin: what the evidence actually shows. https://evidencebased.info/interventions/melatonin. Updated 2026-07-16.
BibTeX
@misc{substrate_terventionsmelatonin,
  author = {Substrate editorial},
  title  = {Melatonin: what the evidence actually shows},
  year   = {2026},
  url    = {https://evidencebased.info/interventions/melatonin},
  note   = {evidencebased.info}
}