Health · Friday, September 11, 2026 · 6
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Long-term melatonin use linked to higher heart failure risk in insomnia patients
A new study presented at the American Heart Association's Scientific Sessions 2025 found that adults with chronic insomnia who used melatonin for a year or more had roughly a 90% higher chance of developing heart failure over five years. The observational findings do not prove causation but raise safety questions about a supplement widely seen as harmless.
Bottom line — The study of 130,828 insomnia patients found a 90% higher heart failure risk among long-term melatonin users.
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- The analysis, using TriNetX electronic health records, compared insomnia patients with at least 12 months of documented melatonin use to those with none, per the American Heart Association.
- Heart failure occurred in 4.6% of the melatonin group versus 2.7% of the comparison group, according to the study presented at AHA Scientific Sessions 2025.
- Hospitalisation for heart failure was nearly 3.5 times higher among long-term users (19.0% vs 6.6%), and all-cause mortality was also elevated (7.8% vs 4.3%), the researchers reported.
- Lead author Dr Ekenedilichukwu Nnadi stressed that the findings 'do not prove a direct cause-and-effect relationship' and that more research is needed, per the AHA press release.
- A key limitation: melatonin is prescription-only in the UK but available over the counter in the US, meaning actual use may be undercounted in the records, the study authors noted.
- Dr Marie-Pierre St-Onge, a sleep researcher not involved in the study, said she was surprised physicians would prescribe melatonin for insomnia for over a year, as it is not indicated for that condition in the US, per the AHA.
- Chronic insomnia itself is linked to cardiovascular problems, and the study could not fully separate the effects of melatonin from underlying sleep severity or psychiatric conditions, the researchers acknowledged.
- Some earlier randomised trials have suggested melatonin might even benefit heart failure patients, but those results were not consistent, according to a 2026 systematic review cited by Psychology Today.