A new study raises questions about long-term melatonin use

new Preliminary study It raises concern about long-term use of melatonin supplements among people with chronic insomnia. The research, presented in November at the American Heart Association Scientific Sessions 2025 in New Orleans, suggests that using melatonin for a year or more may be associated with an increased risk of heart problems.

The study has not been peer-reviewed, so the results should be viewed as early evidence, not final answers. The findings highlight the need for more research into how melatonin affects long-term health.

What the study found

Researchers reviewed five years of electronic health records for 130,828 adults diagnosed with insomnia. The average age was 55.7 years, and about 61% were women. They compared people who used melatonin long-term, meaning at least 12 months recorded in their medical record, with similar adults who had insomnia but had no history of melatonin use.

The main analysis found that adults with chronic insomnia who used melatonin long-term had a 90% higher chance of developing heart failure over five years than adults who did not take melatonin (4.6% vs. 2.7%).

The study also found that people taking melatonin were approximately 3.5 times more likely to be hospitalized for heart failure than those not taking it (19.0% vs. 6.6%).

The researchers noted some limitations. The database included countries where melatonin requires a prescription and places like the United States where it does not. Because the study relied on documented prescriptions and medication use, many people taking melatonin without a prescription would be considered nonusers. This means that results may not fully reflect real-world use.

What is melatonin?

Melatonin It is a hormone that your body naturally produces. It helps regulate the sleep-wake cycle by indicating that bedtime is approaching.

Melatonin supplements are widely available in the United States, and over-the-counter supplements are available in doses ranging from 1 to 10 milligrams. However, because melatonin is sold as a dietary supplement, it is not regulated by the Food and Drug Administration. This means that the content of the supplement may differ from what is listed on the product label.

A 2017 study Found in the Journal of Clinical Sleep Medicine that the melatonin content in nutritional supplements often varies significantly from what is listed on the label. The results showed that the melatonin content in more than 71% of the supplements differed from the label by more than 10%, ranging from 83% less to 478% more than stated on the label. The levels even varied from batch to batch within the same brand.

Melatonin can definitely be effective Circadian rhythm disordersbut there is little evidence that it works well as a general sleep aid. However, many people use it to self-treat insomnia.

Increasing use and safety guidelines

Melatonin use has increased in the past two decades at all ages, a trend that supports it research Shows significant growth in reported supplement use among US adults from 1999 through 2018.

In the wake of the pandemic, there has been a significant rise in emergency calls related to melatonin overdoses in children. In response, the American Academy of Sleep Medicine issued a Health consultation Urge parents to seek medical guidance before giving melatonin to children or teens.

Experts continue to emphasize caution, especially since the content of supplements varies widely and long-term effects remain unclear.

Understanding insomnia

Since many people take melatonin to treat insomnia, it is helpful to understand what insomnia is and how it is usually treated.

Chronic insomnia It means having trouble sleeping at least three times a week for three months or more. About 10% of adults suffer from it.

Treatment depends on the cause, but sleep specialists recommend trying Healthy sleeping habits Firstly, for short-term insomnia. However, for chronic insomnia, lifestyle changes are often not enough.

American Academy of Sleep Medicine recommend Cognitive behavioral therapy for insomnia, or CBT-I, as first-line treatment for chronic insomnia in adults. Cognitive behavioral therapy-I Includes strategies for changing unhelpful thoughts and behaviors around sleep. Medications are generally reserved for people who cannot participate in CBT-I, who still have symptoms after treatment, or who need short-term help with CBT-I.

Key takeaways

This new study found an association between long-term melatonin use and heart risk. Melatonin has not been shown to cause heart failure. More research is needed before experts can determine whether long-term melatonin use affects heart health.

Melatonin may seem like a simple solution to sleep problems, but it’s not without risks, and it may not help with insomnia in the first place. If you have chronic sleep problems, talk to a health professional or get help from a hospital sleep team Certified sleep center.

Medical review by Helena Schotland, MD

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Written by: Kate Robards