Stimulant medications have been previously reported as the cause of adverse psychiatric symptoms in children, including mania and psychosis.1 New work by MacKenzie et al. in this month’s Pediatrics ( 10.1542/peds.2015-2486) provides new insight into a subpopulation apparently at very high risk for this concerning side effect. Children diagnosed with ADHD and treated with stimulants, whose parent or parents have major depressive disorder, bipolar disorder or schizophrenia, have a significantly greater risk of psychotic symptoms than their peers.