Obsessive–compulsive disorder
In Europe from the 14th to 16th centuries, it was thought that people who had obsessive thoughts were possessed. They would treat these people by performing sometimes dangerous exorcisms to remove the Devil or evil spirit from the person. In the 1910s, a doctor named Sigmund Freud said that obsessive–compulsive disorder was because of fighting in someone's head. He said that these fights start in childhood when someone gains a "touching phobia", which fights with the natural want to touch things.