Young users of ADHD drugs who have a parent with a history of mental illness have a greater risk of psychotic side effects, according to a study published in the journal Pediatrics. Nearly 2/3 of the 141 study subjects prescribed stimulant medications had a psychotic side effect. These side effects included hallucinations, delusions, hearing voices, and/or perceptual disturbances. Of those who had not taken a stimulant drug, only 1/4 were affected. Via HealthDay.com. Posted December 31, 2015.