Evidence explainerSleep & Magnesium
Melatonin and Heart Failure: What the 2025 Study Showed, and What It Could Not
A 2025 American Heart Association conference abstract linked long-term melatonin records to more heart failure. It is not peer-reviewed, it cannot show cause, and a 2026 national survey analysis found no significant association.
Key takeaways
- The abstract reviewed 5 years of health records for 130,828 adults with insomnia; those with 12+ months of recorded melatonin use had more new heart failure (4.6% vs 2.7%) than matched non-users [6][1].
- The AHA says abstracts at its meetings are not peer-reviewed and are preliminary until published in full; the authors say the study cannot prove cause and effect [1].
- Over-the-counter melatonin users in countries such as the US could have been counted as non-users, and insomnia severity and psychiatric conditions were not captured [1].
- A 2026 analysis of NHANES 1999-2018 found recent melatonin use was not significantly associated with heart failure or composite cardiovascular disease [2].
- Melatonin's sleep benefit in trials is small: about 7 minutes faster sleep onset and 8 minutes more sleep [3].
What the abstract found
Researchers used the TriNetX database to compare adults with chronic insomnia whose records showed melatonin use for at least a year with matched adults who never had melatonin recorded [6][1]. Over 5 years, incident heart failure was 4.6% vs 2.7%, heart failure hospitalization 19.0% vs 6.6%, and death from any cause 7.8% vs 4.3% [1].
Requiring at least 2 melatonin prescriptions 90 days apart gave a similar result (82% higher heart failure risk) [1].
Why it does not settle the question
It is a conference abstract, labeled by the AHA as not peer-reviewed [1]. It is observational, so people who need sleep aids for longer may differ from those who do not in ways that also raise heart risk; the lead author named worse insomnia, depression or anxiety, and other sleep medicines as possible confounders [1].
Melatonin exposure came only from medical records, so anyone buying it over the counter in the US would have landed in the comparison group [1].
The counterpoint from national survey data
An Open Heart analysis of US adults in NHANES (1999-2018) found melatonin users differed markedly from non-users, especially in sleep disturbance and depression; after adjustment, recent use was not significantly associated with heart failure or cardiovascular disease [2].
The authors describe their result as hypothesis-generating: it does not prove benefit or safety, and it does not establish harm [2].
What to do with this
In the US melatonin is not indicated for treating insomnia [1], and its average benefit in trials is small [3]. For chronic insomnia, CBT-I is the recommended first step [4]. If you take melatonin nightly for months, tell your clinician, as the AHA expert quoted on the study advised against chronic use without a proper indication [1].
Gummies are a separate problem: label accuracy is poor [5]. See our gummy label guide and dose and timing guide.
Quick answers
Should I stop taking melatonin?
The evidence does not show melatonin causes heart failure [1][2]. If you use it nightly long term or have heart disease, review it with your clinician.
Was the study published?
As of October 10, 2026 we cite the AHA's release of the 2025 research abstract, which the AHA labels not peer-reviewed [1].
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References
- [1]Long-term use of melatonin supplements to support sleep may have negative health effects (AHA Scientific Sessions 2025, Abstract MP2306; research abstract, not peer-reviewed). American Heart Association Newsroom, 2025.
- [2]Melatonin and cardiovascular risk: an NHANES reality check after recent heart failure concerns. Open Heart, 2026.
- [3]Meta-analysis: melatonin for the treatment of primary sleep disorders. PLoS One, 2013.
- [4]Management of Chronic Insomnia Disorder in Adults: A Clinical Practice Guideline From the American College of Physicians. Ann Intern Med, 2016.
- [5]Quantity of Melatonin and CBD in Melatonin Gummies Sold in the US. JAMA, 2023.
- [6]Abstract 4371606: Effect of Long-term Melatonin Supplementation on Incidence of Heart Failure in Patients with Insomnia (conference abstract, not peer-reviewed). Circulation (AHA Scientific Sessions 2025 abstract supplement), 2025.