Obsessive-compulsive disorder (OCD) is an anxiety disorder that usually begins in adolescence or early adulthood but may begin in childhood. When OCD starts in childhood, it is more common in boys than in girls. The usual time of onset is later for females than males, so the disorder is equally common among adult men and women. Without treatment, OCD usually follows a chronic course, and some persons become severely disabled by it. This Patient Page is based on one published in the October 27, 2004, issue of JAMA.