http://www.webmd.com/mental-health/dissociative-identity-disorder-multiple-personality-disorder
Dissociative identity disorder (previously known as multiple personality disorder) is thought to be an effect of severe trauma during early childhood, usually extreme, repetitive physical, sexual, or emotional abuse.
What Is Dissociative Identity Disorder?
Most of us have experienced mild dissociation, which is like daydreaming or getting lost in the moment while working on a project. However, dissociative identity disorder is a severe form of dissociation, a mental process which produces a lack of connection in a person’s thoughts, memories, feelings, actions, or sense of identity. Dissociative identity disorder is thought to stem from trauma experienced by the person with the disorder. The dissociative aspect is thought to be a coping mechanism — the person literally dissociates himself from a situation or experience that’s too violent, traumatic, or painful to assimilate with his conscious self.
