Take Melatonin Every Night? A New Study Warns Of This Surprising Risk

Reported by MindBodyGreen.

Melatonin has long enjoyed an almost untouchable reputation — natural, harmless, the supplement you grab without a second thought when sleep won't come. New research is complicating that story in a significant way.

A study presented at the American Heart Association's 2025 Scientific Sessions analyzed over five years of health records from more than 130,000 adults with diagnosed insomnia, comparing cardiovascular outcomes between those who took melatonin for at least a year and those who didn't. The numbers, according to MindBodyGreen, are hard to ignore: long-term melatonin users were nearly 90% more likely to develop heart failure than non-users (4.6% vs. 2.7%), more than three times as likely to be hospitalized for it (19% vs. 6.6%), and nearly twice as likely to die from any cause over the study period (7.8% vs. 4.3%). "It was striking to see such consistent and significant increases in serious health outcomes, even after balancing for many other risk factors," said lead author Ekenedilichukwu Nnadi, M.D.

Before You Panic, Read the Fine Print

This is association data — not proof that melatonin is literally breaking hearts. The nuance matters. Chronic insomnia on its own is independently linked to elevated cardiovascular risk, meaning people who rely on melatonin nightly for a year or more may already carry a heavier health burden. There's also a methodological wrinkle: since melatonin is prescription-only in many countries, the study's classification system may have mislabeled a large number of U.S. over-the-counter users as non-users — which could distort the gap between groups. Still, Nnadi noted, "if our study is confirmed, this could affect how doctors counsel patients about sleep aids."

The consensus among experts has generally held that short-term, appropriately dosed melatonin — think occasional jet lag, not a nightly ritual — carries minimal risk. What this research challenges is the cultural habit of treating it like a benign long-game solution. It isn't designed for that, and the data is starting to reflect why.

If your sleep needs a real overhaul, the fundamentals still lead: a cool, dark room, reduced screen time before bed, and cutting late-night alcohol. For supplemental support, magnesium is the stronger long-term candidate — roughly 43% of people are already deficient, and it works by activating GABA receptors that calm an overactive nervous system, making it easier to fall and stay asleep without the cardiovascular question marks now trailing melatonin.

The bottom line: melatonin isn't something to fear in the short term, but using it as a nightly default for months or years deserves a real conversation with your doctor — not just a spot in your bedside drawer.

Read the original at MindBodyGreen.