Four Things The Media Didn’t Tell You About The Melatonin Warning Study

A recent study found that people who use melatonin are more likely to diagnosed with heart problems. The media was all over the bad news, but they neglected to tell their readers about the limitations and design flaws of the study.

The study, which was presented at the 2025 American Heart Association Scientific Sessions, concluded that people who had used melatonin for more than a year were 90% more likely to be diagnosed with heart failure (4.6% versus 2.7%) over a 5 year period. Secondary analysis found that the risk of being hospitalized for heart failure was nearly 3.5 times greater, and the risk of death from any cause was nearly double.

The surprising results were presented everywhere in the media. But the media failed to tell their readers about some obvious and important limitations of the study.

Most importantly, the study is not a published or peer reviewed study. Though the press headlines did not include this important detail, the American Heart Association press release included it right at the top in their “Research Highlights.” Though the press didn’t tell their readers, the AHA told the press that “The study featured in this news release is a research abstract. Abstracts presented at American Heart Association’s scientific meetings are not peer-reviewed, and the findings are considered preliminary until published as full manuscripts in a peer-reviewed scientific journal.”

That might have been nice to know. The media would have been all over that caveat if the study had claimed to show that melatonin helps people with insomnia, jet lag, migraine, tinnitus, IBS, GERD, cancer, COVID, blood vessel function, high blood pressure and cognition in people with Alzheimer’s: which it does.

Secondly, the study had a deceptive design. The study included both countries in which melatonin requires a prescription and countries in which it is used over-the-counter. In this study, melatonin use only included prescribed melatonin. That means that, as the press release clearly said, “everyone taking it as an over-the-counter supplement in the U.S. or other countries that don’t require a prescription would have been in the non-melatonin group.” So, some of the safe non-melatonin use comparison was really melatonin use, potentially seriously skewing the conclusion. “The analysis,” the AHA press release says, “may not accurately reflect this.”

The third limitation is that people who are prescribed melatonin may have a doctor prescribe it because their insomnia is more severe. But that could bring with it more severe depression or anxiety or use of other sleep medicines that could be the causes of the heart disease. The press release warns that “Worse insomnia, depression/anxiety or the use of other sleep-enhancing medicines might be linked to both melatonin use and heart risk.”

And, finally, the association with heart disease may be accidental. People who are prescribed melatonin, instead of choosing it for themselves, may actually need melatonin because their circadian rhythm is throwing off their sleep. Circadian rhythm is crucial for sleep, and melatonin regulates the circadian rhythm. But it could be the altered circadian rhythm, and not the melatonin, that is responsible for the increased risk of heart disease, since circadian rhythms are vital for healthy cardiovascular function (JAMA Netw Open. 2025;8(10):e2539031).

That is why a recent study found that light exposure at night, which disrupts melatonin and, therefore, circadian rhythm, increases the risk of coronary artery disease by 32%, heart attack by 47%, heart failure by 56%, arterial fibrillation by 32% and stroke by 28%.

Melatonin has a research record for helping heart health and a long pedigree of safety. That doesn’t mean this new study should be ignored. But it does mean it should be placed in the larger context of melatonin research. And it does mean that the press should have told the public what the press release told the press.