They grunt, claw, and feel their body is covered with hair and their nails are elongated — some people strongly believe they are in the process of metamorphosis into a wolf. There have been 13 case reports of such people since 1850, one psychiatrist has found.Intrigued by treating a patient who thought he was a werewolf, Dr. Jan Dirk Blom, an assistant professor of psychiatry at the University of Groningen, in the Netherlands, mined the archives of psychiatry to find out just how common the condition is.

read more: Werewolf Delusion Even Less Common Than Scientists Thought.