What Causes Someone to Have Multiple Personalities?

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Dissociative identity disorder (DID), previously called multiple personality disorder or split personality disorder, is a complex, post-traumatic, developmental disorder that affects approximately 1% of the general population.

A person with DID presents with different identities. The person often is unaware these other identities exist and is unable to remember what took place when another identity was in control. They may encounter people who know them but whom they don't recall meeting, find things they have purchased without remembering, be unaware of how they got to a location, or experience a sense of amnesia or missing time.

An illustration with common symptoms of dissociative identity disorder (DID)

Verywell / Sydney Saporito

DID is almost always the result of childhood trauma. While it always develops during childhood, it may begin to manifest in adulthood, usually as a result of stresses or triggers.

Read on to learn more about what causes DID.

What Is Dissociative Identity Disorder?

According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), DID is a mental health condition in which a person has two or more distinct identities that alternate appearing, or being "in control." They each have their own sense of self and sense of agency, affect (outward expression of emotions), behaviors, consciousness, memory, perception, cognition, and/or sensory-motor functioning. These differences are sometimes, but not always, observable to others.

A person with DID typically does not remember what occurred when another identity was presenting. The person will have gaps of missing time, being unable to remember events and other details that occurred during those times.

While the person with DID may not remember after another identity has taken over, the other identities have their own agency (acting independently and making their own choices), will, and perspective.

What Are the Symptoms of Dissociative Identity Disorder?

People with DID may show symptoms associated with mood, anxiety, and personality.

Some symptoms of DID may include:

  • Inability to remember large parts of childhood
  • Episodes of memory loss or "lost time," for instance, finding themselves somewhere they don't remember getting to, or in possession of items they don't recall buying.
  • Sudden return of memories (flashbacks)
  • Periods of feeling disconnected or "detached" from their body and thoughts or having out-of-body experiences
  • Hallucinations (sensory experiences that are not based in reality)
  • Differences in handwriting from one time to another
  • Changing levels of functioning
  • Thoughts or actions of suicide or self-harm

Help Is Available

If you are having suicidal thoughts, contact the National Suicide Prevention Lifeline at 988 for support and assistance from a trained counselor. If you or a loved one are in immediate danger, call 911.

If you or a loved one is struggling with dissociation or dissociative identity disorder, contact the Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline at 800-662-4357 for information on support and treatment facilities in your area.

For more mental health resources, see our National Helpline Database.

Other symptoms and conditions associated with DID include:

  • Depression
  • Mood swings
  • Anxiety and related symptoms and conditions
  • Eating disorders
  • Sleep difficulties
  • Headaches and body pains
  • Sexual dysfunction

What Causes Dissociative Identity Disorder?

DID is almost always associated with recurrent childhood trauma, such as abuse or neglect. One study showed 86% of the sample of people with DID reported a history of sexual abuse.

Some factors believed to be involved in the development of DID include:

  • Severe, recurrent childhood trauma, including physical, emotional, or sexual abuse
  • The lack of safe and nurturing resources to respond to and manage trauma
  • The child's ability to dissociate easily
  • Dissociation, or "splitting," as a defense mechanism against the trauma and a survival skill

A child who experiences ongoing trauma may tell themselves, "That's not me; that's someone else" as a response to the overwhelming fear they are experiencing. This detaches these thoughts and feelings from themselves and places them onto "someone else", even though that other individual is still part of them.

Dysfunctional attachment to caregivers may also contribute to the development of DID.

Disorganized attachment (in which an infant or child is both frightened of and seeks comfort and security from a primary caregiver) or betrayal trauma (in which someone the child relies on causes them trauma), can prompt the child to dissociate as an adaptive response. This compartmentalization lets the child maintain attachment to an abusive or neglectful person who is also vital to their survival and development.

Can DID Develop in Adulthood?

DID almost always develops in childhood, but it may not become apparent or manifest as multiple identities until later in adolescence or adulthood.

Mode Theory

Dissociative identities can result from a breakdown between how experienced events are encoded (as part of memory) and a sense of ownership of those memories. Different identities take on ownership of these memories and how they respond to them.

How and why these different ways of encoding occur may be due to the theory that personality is made up of "modes" containing cognitive, affective, behavioral, and physiological representations, or schemas.

These modes influence how a person responds to internal and environmental demands. For example, a woman may have a "mother" mode who determines how she thinks, feels, and experiences when caring for her child. She may also have a "boss" mode, a "wife" mode, a "daughter" mode, and other modes that all influence how she feels and interacts in different situations.

Usually, a person can incorporate all of these modes into one "conscious control system" that gives an overall sense of self. When switching between modes, most people are still aware of the other modes and are able to accept that each of these modes integrates into who they are as one person.

DID can arise when these modes become disconnected from each other, creating smaller, isolated pockets. For example, modes associated with families, such as mother and partner, may become detached from those associated with work.

This creates multiple conscious control systems, each with its own aspect of self that is based on the modes they are comprised of. This then gives rise to distinct, first-person perspectives.

Can DID Be "Faked"?

Theories exist that DID could be caused by suggestion, fantasy, or role-playing. These theories are not supported by evidence, and trauma researchers repeatedly challenge this myth.

Brain Differences

People with DID have been found to have some alterations in their brain morphology (structural measures of the brain such as volume and shape).

The amygdala (part of the brain involved in the input and processing of emotions) and the hippocampus (part of the brain involved in learning and memory) have also been found to be affected in people with DID. Studies have also shown a reduction in functioning and blood flow in the orbitofrontal cortex (the front area of the brain) in people with DID.

People with DID also show smaller volumes in the parietal structures (located in the upper back area of the skull) involved in perception and personal awareness, and frontal structures involved in movement execution and the learning of fear. Increased white matter tracts involved in information communication between certain areas of the brain (somatosensory association areas, basal ganglia, and the precuneus) have also been noted in people with DID.

How Is Dissociative Identity Disorder Associated With Trauma?

DID is heavily associated with childhood trauma. Among people with DID in the United States, Canada, and Europe, about 90% experienced childhood abuse and neglect.


DID is a mental health condition in which two or more identities exist within one person.

DID is almost always a response to severe and ongoing childhood trauma, such as abuse or neglect.

Structural brain differences have also been noted in people with DID.

A Word From Verywell

If you are experiencing signs of DID, it's important to seek help from a healthcare provider or mental health professional. Getting an accurate diagnosis is the first step on the road to healing from your past trauma, and managing your symptoms.

Frequently Asked Questions

  • Is multiple personality disorder real?

    Dissociative identity disorder is a real mental health condition that is outlined in the DSM-5. On-going studies continue to confirm its validity.

  • Is dissociative identity disorder genetic?

    Currently, there is no direct evidence to show that DID is genetic, but there may be a genetic link that has not yet been identified.

  • Are there movies that feature someone with multiple personalities?

    Portrayals of DID are common in movies, books, and television shows, but they are rarely accurate. Unfortunately, this creates a lot of misconceptions about the condition and the experiences of people who live with it.

  • How should you respond to someone with split personalities?

    "Switching" to one of the alter identities, sometimes abruptly, can make your friend or loved one sound and act differently. If they don't know who you are, introduce yourself and reassure them in they are frightened.

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  6. Şar V, Dorahy MJ, Krüger C. Revisiting the etiological aspects of dissociative identity disorder: a biopsychosocial perspective. Psychol Res Behav Manag. 2017;10:137-146. doi:10.2147/PRBM.S113743

  7. American Association for Marriage and Family Therapy. Dissociative identity disorder.

  8. McLean Hospital. Everything you need to know about dissociative identity disorder.

  9. Schlumpf YR, Reinders AATS, Nijenhuis ERS, Luechinger R, Osch MJP van, Jäncke L. Dissociative part-dependent resting-state activity in dissociative identity disorder: a controlled fmri perfusion study. PLoS One. 2014;9(6):e98795. doi:10.1371/journal.pone.0098795

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By Heather Jones
Heather M. Jones is a freelance writer with a strong focus on health, parenting, disability, and feminism.