New data shows that Americans’ use of the over-the-counter sleep aid melatonin has increased significantly over the last 20 years. In the study, published last week in the Journal of the American Medical Association, researchers from the Mayo Clinic and China found that by 2018 Americans were taking more than twice the amount of melatonin they took a decade earlier. Also, a larger percentage of melatonin users were taking doses far higher than the 5 mg doses recommended for jet lag and difficulty sleeping. While generally safe for short-term use, melatonin has been linked to headache, dizziness, nausea, confusion, irritability, depression and low blood pressure. Plus, the researchers warn that the actual amount of melatonin in some of the supplements on the market might actually be 500 percent higher than what’s listed on the label.