Melatonin May Not Be as Harmless as We Thought

For years, melatonin has been marketed as a gentle, natural aid in helping people fall asleep faster. However, new research presented at the American Heart Association’s Scientific Sessions is raising concerns about the long-term effects of taking it.

A large-scale analysis of more than 130,000 adults with insomnia found that those prescribed melatonin for over a year were 89% more likely to develop heart failure and twice as likely to die from any cause over five years, compared to those who didn’t take it.

The study led by Ekenedilichukwu Nnadi, MD, at SUNY Downstate/Kings County Primary Care used real-world data from the TriNetX Global Research Network, covering patients in the U.S. and U.K. After rigorously matching participants by age, health history, and other factors, researchers found striking differences:

• Heart failure diagnoses: 4.6% of melatonin users vs. 2.7% of non-users
• Heart failure hospitalizations: 19% vs. 6.6%
• All-cause mortality: 7.8% vs. 4.3%

While these results don’t prove melatonin causes heart problems, they challenge its reputation as a harmless, over-the-counter sleep fix. “If our study is confirmed, this could affect how doctors counsel patients about sleep aids,” said Dr. Nnadi.

Experts caution that the findings are preliminary and haven’t been peer-reviewed yet. However, even skeptics agree that the associations are serious enough to warrant further investigation. Carlos Egea, president of the Spanish Federation of Sleep Medicine Societies, called for randomized controlled trials to clarify melatonin’s cardiovascular safety profile.

For now, public health professionals emphasize moderation. Short-term use, typically one to two months, is considered safe for most adults. However, in the long term, unsupervised use may carry risks that we’re only beginning to understand.

As melatonin use skyrockets, especially among adults and children, this research is a timely reminder that “natural” doesn’t always mean “risk-free.”