In recent days, several media outlets have reported on a study linking prolonged use of melatonin with a higher risk of heart failure. The headlines have been eye-catching — and, in some cases, alarmist — causing concern among those who use this supplement to improve their sleep.
But what does the science actually say? And should we be worried about melatonin use?
What the Melatonin Study Found
The study, presented at the American Heart Association (AHA) conference in November 2025, analyzed data from more than 130,000 people diagnosed with insomnia. In this group, those who had used melatonin for at least one year showed higher rates of heart failure, hospitalization, and mortality than those who did not use it.
The findings have received wide attention because:
• The sample size is very large.
• The numerical differences appear relevant (approx. 4.6% vs. 2.7% heart failure over 5 years).
• Melatonin is a very popular supplement, perceived as “natural” and safe.
But Be Careful: Association Is Not Causation
Although the study provides interesting information, it does not prove that melatonin causes heart failure.
Here are some key points acknowledged by the authors themselves and the AHA:
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It is an observational study, not a clinical trial. It only detects associations, not cause-and-effect.
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Lack of information on actual dose and duration. It is unclear how much each person took or whether use was continuous.
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Unrecorded over-the-counter use. In many countries, melatonin is freely available, so some “non-users” may actually have been taking it.
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Possible confounding factors. People with more severe insomnia, anxiety, or chronic diseases may already have a higher cardiovascular risk.
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It has not been peer-reviewed. For now, it is an abstract presented at a conference, not a fully published study.
In other words, the accurate headline would be:
“An observational study finds an association between long-term melatonin use and higher risk of heart failure, but does not prove causality.”
How to Interpret This Information
Melatonin remains a supplement with an excellent safety profile when used correctly, especially for:
• Short-term use to adjust the circadian rhythm (e.g., jet lag or shift work).
• Low physiological doses (0.5–2 mg) that mimic the body’s natural levels.
We should be more cautious in cases of:
• Long-term use without medical supervision.
• High doses taken for months or years.
• People with cardiovascular or metabolic diseases who already have an increased risk.
The Real Message: Responsible Use, Reliable Information
This type of news should help promote responsible supplement use, not generate unjustified fear.
In fact, millions of people take much stronger sleep medications, such as benzodiazepines or hypnotics, without the same media coverage — even though their risk profile is far higher than melatonin’s.
The key lies in consumer education and transparency:
• Informing about when and how to use melatonin safely.
• Avoiding messages suggesting absolute safety or universal benefit.
• Always recommending medical consultation for long-term use or in the presence of health conditions.
In Summary
• Yes, the study exists and suggests a possible association between long-term melatonin use and heart failure.
• No, it does not prove that melatonin is the cause.
• Yes, further research and responsible use are advisable.
• No, there is no reason for alarm among those using it occasionally or under professional guidance.
In science, headlines sell — but nuance protects.
And in health, nuance matters.
References
- American Heart Association (AHA). Long-term use of melatonin supplements to support
sleep may have negative health effects. Newsroom. 4 noviembre 2025. Available at:
https://newsroom.heart.org/news/long-term-use-of-melatonin-supplements-to-support-sleep-
may-have-negative-health-effects -
Science Media Centre Spain. Long-term use of melatonin for insomnia linked to higher risk of heart failure. November 4, 2025. Available at:
https://sciencemediacentre.es/el-uso-continuado-de-melatonina-para-el-insomnio-se-
relaciona-con-un-mayor-riesgo-de-insuficiencia -
Andersen, L.P., et al. (2016). The Safety of Melatonin in Humans. Clin Drug Investig. 36(3):169–75.
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Sánchez-Barceló, E. J., et al. (2011). Clinical uses of melatonin: evaluation of human trials. Current Medicinal Chemistry, 18(36), 5471–5495.
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Brzezinski, A., et al. (2005). Effects of exogenous melatonin on sleep: a meta-analysis. Sleep Medicine Reviews, 9(1), 41–50.
