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Mel9.0
Melatonin Research
Likely helpsHigh safety
53 peer-reviewed studies
What the evidence says
Likely helps
Melatonin appears to help in 14 of 19 studies with measurable effects — the evidence leans clearly favourable.
Most evidence is from high-quality meta-analyses and randomised trials published 2002–2026 with a typical study size of 189 participants.
Based on 53 studies · 27 meta-analyses · 11 RCTs · 29,039 total participants
Confidence
High
What the studies found
14helped4unclear1didn't help· 34 more without graded effect data
By outcome
Sleep & insomniaReduces sleep latency by 7-12 minutes · 30-60 minutes · Modest improvement with extended-release forms · 1 week · Modest improvement in slow-wave sleep architecture · 1-2 weeks
Fertility & reproductiveMay support reproductive health and fertility markers · 4-12 weeks
Too few graded studies1 study
By the numbers
Pulled from 45 studies with measurable effects
Likely real effects
90%
across studies
People studied
29k
typical study: 189 people
Strongest designs
38
27 pooled, 11 randomised
Showed benefit
74%
14/19 studies
How long studies ran
1–3 months
1
3+ months
2
Populations Studied
Adults with sleep disorders2
Patients with dementia2
General population2
Mild cognitive impairment and mild Alzheimer's disease patients1
Active research area
48 studies in the last 5 years · Latest meta-analysis: 2025
200220142026
1Cognitive function in mild cognitive impairment and Alzheimer'sMeta-AnalysisCited 18×n=4,599 · very large study2024
Melatonin may be a better potential disease-modifying treatment for cognitive decline in mild AD and MCI.
Terao I et al. · Journal of Alzheimer's disease : JAD (2024)
Melatonin may be a better potential disease-modifying treatment for cognitive decline in mild AD and MCI.
Aerobic exercise for a short time might also be better than donanemab, lecanemab and aducanumab if continued, as it is well tolerated and more effective, although less valid due to heterogeneity.
Another limitation is the small number of participants.
2Insomnia symptomsMeta-AnalysisCited 17×n=4,875 · very large study2023
PR melatonin for individuals with a mean age ≥ 55 and ramelteon show larger effect sizes.
Maruani J et al. · Journal of sleep research (2023)
For the subgroup mean age of patients ≥55, PR melatonin was efficacious on oSE with a large effect size (p < 0.001; weighted difference = 2.95%).
Regarding long-term effects, ramelteon has a large effect size on oTST (p < 0.001; weighted difference = 2.02 min) and sTST (p < 0.001; weighted difference = 14.5 min).
PR melatonin and ramelteon appear efficacious compared with placebo for insomnia symptoms with PR melatonin showing mostly small to medium effect sizes.
3Delirium prevention and mortality reductionMeta-AnalysisCited 7×n=4,850 · very large study2023
This study provides evidence of the potential effects of MRAs in preventing delirium and reducing mortality.
Wada M et al. · General hospital psychiatry (2023)
Barely noticeable benefit
← WorseNo effectBetter →
Likely real
Additionally, MRAs were associated with a significant reduction in mortality rate (risk ratio = 0.90, p = 0.02) in delirium prevention studies.
This study provides evidence of the potential effects of MRAs in preventing delirium and reducing mortality.
Further research is required to elucidate the therapeutic potential of MRAs for delirium and identify specific patient populations that may benefit from this agent.
7Manic symptoms in bipolar disorderMeta-AnalysisCited 22×n=1,279 · large study2022
There is a paucity of studies examining pharmacological interventions for sleep and circadian rhythm disturbance in BD.
McGowan NM et al. · CNS drugs (2022)
No clear effect
← WorseNo effectBetter →
The largest efficacy signal detected was for manic symptoms (four studies; g = - 0.44 [95% CI - 1.03 to 0.14]) but there was substantial heterogeneity between studies and patient characteristics.
There is a paucity of studies examining pharmacological interventions for sleep and circadian rhythm disturbance in BD.
Few studies assessed sleep-related symptoms, and none quantitatively examined endogenous melatonin patterns or other circadian rhythms.
9Fatigue incidence in cancer patientsMeta-AnalysisCited 3×n=126 · medium study2025
The available evidence is of very low certainty, so we are unable to draw conclusions about the effects of melatonin on quality of life and sleep at three months in people receiving treatment for cancer.
Yu ZY et al. · The Cochrane database of systematic reviews (2025)
Huge benefit
← WorseNo effectBetter →
We downgraded the certainty of the evidence because of high risk of bias, small sample size, the width of the 95% confidence interval, and indirectness due to inadequate reporting of cancer type.
Melatonin likely reduces the incidence of fatigue (RR 0.46, 95% CI 0.39 to 0.55; 10 studies, 1359 participants; moderate-certainty evidence) and may reduce nausea (RR 0.85, 95% CI 0.72 to 1.00; 6 studies, 710 participants; low-certainty evidence).
We downgraded the certainty of the evidence because of the high risk of bias and the width of the 95% confidence interval.
Thus, melatonin, by increasing psychologic parameters and cardiac potency, could be advised as a novel drug for treatment and palliating heart failure patients.
Daliri AS et al. · Clinical cardiology (2025)
As the effect of melatonin, fatigue, and NT-Pro BNP were reduced but on the contrary sleep quality, appetite, and FMD (Flow-Mediated Dilation) significantly increased.
Thus, melatonin, by increasing psychologic parameters and cardiac potency, could be advised as a novel drug for treatment and palliating heart failure patients.
12Total nocturnal sleep timeMeta-AnalysisCited 88×n=222 · medium study2020
We discovered a distinct lack of evidence to guide decisions about drug treatment of sleep problems in dementia.
McCleery J et al. · The Cochrane database of systematic reviews (2020)
No clear effect
← WorseNo effectBetter →
We could synthesise data for two of our primary sleep outcomes: total nocturnal sleep time (TNST) (MD 10.68 minutes, 95% CI -16.22 to 37.59; 2 studies, n = 184), and the ratio of day-time to night-time sleep (MD -0.13, 95% CI -0.29 to 0.03; 2 studies; n = 184).
We found low-certainty evidence that trazodone 50 mg for two weeks may improve TNST (MD 42.46 minutes, 95% CI 0.9 to 84.0; 1 study, n = 30), and sleep efficiency (MD 8.53%, 95% CI 1.9 to 15.1; 1 study, n = 30) in people with moderate-to-severe AD.
The effect on time awake after sleep onset was uncertain due to very serious imprecision (MD -20.41 minutes, 95% CI -60.4 to 19.6; 1 study, n = 30).
Melatonin is a potential antioxidant that may prevent damage from oxidative stress in patients with PCOS.
Ziaei S et al. · Journal of ovarian research (2024)
Melatonin is a potential antioxidant that may prevent damage from oxidative stress in patients with PCOS.
However, the clear effect of melatonin supplementation on cardiometabolic risk factors, hormonal outcomes, and pregnancy-related outcomes needs to be evaluated further in large populations and long-term RCTs.
The present study revealed that melatonin supplementation has a decreasing effect on depression in all duration of studies and doses subgroup and in age more than 65 years in depression studies but heterogenicity of the included studies, did not allow a definitive conclusion.
Shokri-Mashhadi N et al. · Behavioural brain research (2023)
Noticeable benefit
← WorseNo effectBetter →
Melatonin supplementation yielded no significant effect on BDNF concentration (WMD: -5.61; 95% CI: -14.10, 2.88; I-square: 85.6%), but improved depression by decreasing the score (WMD: -0.76; 95% CI: -1.12, -0.4; I-square: 88.0%).
The subgroup analysis showed that melatonin supplementation had a significant decreasing effect on BDNF levels in doses ≤ 10 mg/day, with more than 4 weeks of duration, and in men.
The present study revealed that melatonin supplementation has a decreasing effect on depression in all duration of studies and doses subgroup and in age more than 65 years in depression studies but heterogenicity of the included studies, did not allow a definitive conclusion.
Although melatonin and ramelteon may be effective treatments for delirium, particularly to shorten the duration of delirium and to limit the use of rescue medication, current data is limited in number and in its quality.
Beaucage-Charron J et al. · Journal of psychosomatic research (2023)
Noticeable benefit
← WorseNo effectBetter →
Likely real
Two RCTs reported the duration of delirium and a meta-analysis provided a statistical difference between melatonin and placebo (-1.72 days, 95% CI -2.66 to -0.77, p = 0.0004).
Although melatonin and ramelteon may be effective treatments for delirium, particularly to shorten the duration of delirium and to limit the use of rescue medication, current data is limited in number and in its quality.
Clinicians should wait until higher quality data from ongoing RCTs are available before prescribing melatonin to delirious patients.
18MMSE score in mild stage Alzheimer's diseaseMeta-AnalysisCited 87×2021
Importantly, melatonin significantly improved MMSE score in mild stage of AD [MD: 1.89 (0.96; 2.82) p < 0.0001].
Sumsuzzman DM et al. · Neuroscience and biobehavioral reviews (2021)
Noticeable benefit
← WorseNo effectBetter →
Likely real
Importantly, melatonin significantly improved MMSE score in mild stage of AD [MD: 1.89 (0.96; 2.82) p < 0.0001].
In healthy-subjects, although daytime melatonin treatment notably decreased in accuracy by correct responses [SMD: -0.74 (-1.03; -0.45) p < 0.00001], the reaction-time score on different stimuli (p = 0.37) did not increased.
Meta-analysis of MMSE score suggested that melatonin is effective in treatment for mild stage of AD.
19Sleep onset latency in chronic insomniaMeta-AnalysisCited 42×n=24 · very small study2022
In comorbid insomnia, melatonin significantly improved sleep onset latency in all age groups, but there was only one study in adults group.
Choi K et al. · Sleep medicine reviews (2022)
In comorbid insomnia, melatonin significantly improved sleep onset latency in all age groups, but there was only one study in adults group.
In conclusion, melatonin did not appear to be effective in adults but might be effective in children and adolescents with chronic insomnia for both comorbid insomnia and non-comorbid insomnia.
Further studies are needed to establish the efficacy and safety of melatonin by age groups.
Amino acids, vitamin D and melatonin supplements were significantly beneficial to improve sleep quality.
Chan V et al. · Postgraduate medical journal (2022)
Noticeable benefit
← WorseNo effectBetter →
Subjective sleep quality was significantly improved by supplementation of amino acids (MD -1.27, 95% CI -2.35 to -0.20; I2=0%), melatonin (MD -1.21, 95% CI -2.17 to -0.24; I2=79%) and vitamin D (MD -1.63, 95% CI -3.15 to -0.10; I2=85%).
Amino acids, vitamin D and melatonin supplements were significantly beneficial to improve sleep quality.
However, high heterogeneity and wide confidence levels were observed in vitamin D and melatonin.