American Heart Association

A preliminary analysis of more than 130,000 adults with insomnia has found that those prescribed melatonin for more than a year had an 89 percent higher risk of heart failure and were about twice as likely to die from any cause over a five-year period compared to non-users. The findings, presented at the American Heart Association's Scientific Sessions in November 2025, have not yet been peer-reviewed, but they have already prompted a formal safety signal from Saudi Arabia's drug regulator.