"As Rapaport points out in her book and elsewhere, OCD can occur with other syndromes, ADD being one of them. The symptoms of OCD include driven, ritualistic thinking; compulsive, repetitive behavior; intrusive, unpleasant thoughts; superstitions that control one's behavior; and an inability of the 'will' to counteract these symptoms, try as they might. Like ADD, it is a biologically based disorder." (Hallowell and Ratey 2011)