Children being treated with medication for attention deficit hyperactivity disorder suffer through hallucinations and psychotic symptoms at a higher rate than previously thought, a new study suggests. The study by the U.S. Food and Drug Administration identified more than 850 instances where children being treated for ADHD with drugs like Ritalin, Adderall XR, Focalin and Metadate CD had hallucinations, many times involving snakes, insects and worms crawling on them.