Dissociative personality disorder is also known as multiple personality disorder. It is an extremely complex disorder that results in two or more split identities. Dissociative disorders are mental illnesses that involve disruptions or breakdowns of memory, awareness, identity or perception. It is a condition in which a single person displays multiple distinct identities or personalities each with its own pattern of perceiving and interacting with the environment. The person with Dissociative personality disorder may or may not be aware of the other personality states

Other types of dissociative disorders defined in the DSM-IV are:

1. Dissociative amnesia.
2. Dissociative fugue.
3. Depersonalization disorder.

Dissociation is a key feature of dissociative disorders. Dissociation can serve as a defense mechanism against the physical and emotional pain of a traumatic or stressful experience. By dissociating painful memories from everyday thought processes, a person can use dissociation to get rid of stressful or painful situations. Even after the trauma is long past, however, the leftover pattern of dissociation to escape stressful situations continues. The person also experiences memory loss that is too extensive to be explained by ordinary forgetfulness. Some people with Dissociative Disorders can hold highly responsible jobs, contributing to society in a variety of professions, the arts, and public service — appearing to function normally to coworkers, neighbors, and others with whom they interact daily.