People using melatonin for more than a year faced dramatically higher risks of heart failure and death compared to non-users. Once considered a “natural” sleep fix, melatonin may pose hidden cardiovascular risks that call for closer scrutiny. Credit: Shutterstock Key Research Findings A large review of health data from more than 130,000 adults with insomnia found that people who took melatonin for a year or longer were more likely to develop heart failure, be hospitalized for the condition, or