What is dissociative identity disorder (DID)?

Dissociative identity disorder (DID) was formerly called multiple personality disorder. People with DID develop one or more alternate personalities that function with or without the awareness of the person’s usual personality.


When one or more of these functions is disrupted, dissociative symptoms can result. These symptoms can be mild, but they can also be severe to the point where they interfere with a person’s general functioning, both in personal life and at work.

How common is (DID)?

Instances of true DID are very rare. When they occur, they can occur at any age. Females are more likely than males to get DID.

What causes dissociative identity disorder (DID)?

A history of trauma is a key feature of dissociative identity disorder. About 90% of the cases of DID involve some history of abuse. The trauma often involves severe emotional, physical, and/or sexual abuse. It might also be linked to accidents, natural disasters, and war. An important early loss, such as the loss of a parent or prolonged periods of isolation due to illness, may be a factor in developing DID.

Dissociation is often thought of as a coping mechanism that a person uses to disconnect from a stressful or traumatic situation, or to separate traumatic memories from normal awareness. It is a way for a person to break the connection with the outside world, and create distance from an awareness of what is occurring.

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 maintain a relatively healthy level of functioning, as though the trauma had not occurred.

Episodes of DID can be triggered by a variety of real and symbolic traumas, including mild events such as being involved in a minor traffic accident, adult illness, or stress. Or a reminder of childhood abuse for a parent may be when their child reaches the same age at which the parent was abused.

What are the symptoms of DID?

A person with DID has two or more different and distinct personalities, the person’s usual (“core”) personality and what are known as alternate personalities, or “alters.” The person may experience amnesia when an alter takes control over the person’s behavior.

Each alter has distinct individual traits, a personal history, and a way of thinking about and relating to his or her surroundings. An alter may be of a different gender, have a different name, or a distinct set of manners and preferences. (An alter may even have different allergies than the core person.)

The person with DID may or may not be aware of the other personality states and memories of the times when an alter is dominant. Stress, or even a reminder of a trauma, can trigger a switch of alters.

In some cases, the person with DID may benefit from a particular alter (for example, a shy person may use a more assertive alter to negotiate a contract). More often DID creates a chaotic life and problems in personal and work relationships. For example, a woman with DID may repeatedly meet people who seem to know her but whom she does not recognize or remember ever meeting. Or she may find items around the home that she does not remember buying.

DID shares many psychological symptoms as those found in other mental disorders, including:

  • Changing levels of functioning, from highly effective to disturbed/disabled
  • Severe headaches or pain in other parts of the body
  • Depersonalization (feeling disconnected from one’s own thoughts, feelings, and body)
  • Derealization (feeling that the surrounding environment is foreign, odd, or unreal)
  • Depression and/or mood swings
  • Anxiety
  • Eating and sleeping disturbances
  • Problems with functioning sexuality
  • Substance abuse
  • Amnesia (memory loss or feeling a time distortion)
  • Hallucinations (false perceptions or sensory experiences, such as hearing voices)
  • Self-injurious behaviors such as “cutting”
  • Suicide risk — 70% of people with DID have attempted suicide
