Dissociative identity disorder (formerly called Multiple Personality Disorder or MPD) is defined in the DSM-IV-TR as the presence of two or more personality states or distinct identities that repeatedly take control of one’s behavior. The patient has an inability to recall personal information. The extent of this lack of recall is too great to be explained by normal forgetfulness. The disorder cannot be due to the direct physical effects of a general medical condition or substance.
DID entails a failure to integrate certain aspects of memory, consciousness and identity. Patients experience frequent gaps in their memory for their personal history, past and present. Patients with DID report having severe physical and sexual abuse, especially during childhood. The reports of patients with DID are often validated by objective evidence.