Results from the National Comorbidity Survey Replication found an estimated prevalence of adult attention-deficit/hyperactivity disorder of 4.4%, according to findings published in the American Journal of Psychiatry in 2006. Researchers noted that the estimate is likely conservative, in part because of more subtle symptoms in adults compared with children. Healio.com/Internal Medicine presents the latest research on adult ADHD that physicians should know, including onset of the disorder, risk factors and therapy outcomes.