at one time obsessive or compulsive behavior was thought to indicate demonic possession. exorcism was one of the earliest -- and least successful -- forms of treatment. the traditional hypothesis from freudian theory holds that obsessions reflect unconscious desires from an earlier stage of development. the most widely held theory today suggests that there is a genetic predisposition to ocd and that it is triggered by abnormal brain chemistry. people with ocd often have other psychological problems such as depression eating disorders substance abuse personality disorders attention-deficit disorder or anxiety. they also may suffer from obsessively pulling out their hair (trichotillomania) preoccupation with their appearance (body dysmorphic disorder) and the belief that they have a medical illness (hypochondria). these other problems can make ocd much more difficult to diagnose and treat.
what causes obsessive-compulsive disorder?