WASHINGTON, D.C. — Adderall is an effective treatment for attention deficit hyperactivity disorder (ADHD), but a sharp rise in US prescriptions over the past two decades has sparked concerns among researchers about rare but serious side effects.

In a striking new study published in the American Journal of Psychiatry on Thursday, a team led by psychiatrist Lauren Moran of Mass General Brigham in Boston found that individuals taking high doses of the stimulant face more than a fivefold increased risk of developing psychosis or mania.