How does multiple personality disorder work

Multiple Personality Disorder, also called Dissociative Identity Disorder or Split Personality Disorder is a condition where a person has multiple personalities or identities. These identities tend to think and behave differently.

People with this disorder act like there are two or more people in their heads who occasionally take control of their bodies, making them talk and act differently.

Think of the people who claim to be possessed by evil spirits, be it in horror movies or in real life. When the spirit possesses the body, the person behaves as if they’re under the control of that spirit. They lose their own personality.

A person with Multiple Personality Disorder acts as if they’re possessed by these different personalities that are called alters.

Unlike evil spirits, these alters are real. It’s much more likely that people who claim to be possessed are actually suffering from Multiple Personality Disorder. Exorcism may well have been an age-old therapeutic technique to treat this condition.

Host personality and the alters

First, there’s the core personality called the host. The body actually belongs to the host who has the patient’s given name. This is the person who is suffering from Multiple Personality Disorder. Their alters or alternate personalities have their own distinct names, life histories, behavioral characteristics, manner of speaking, and even voice tone.

For instance, 26-year-old Sally who suffers from Multiple Personality Disorder has two alters- Jamie, a 16-year-old man and Holly, a 6-year-old girl. When Jamie takes over Sally’s body, Sally talks and behaves like a 16-year-old teen and when Holly takes over Sally’s body, Sally talks and acts like a 6-year-old.

The phenomenon of alters taking over the host’s body or the host regaining control of the body is called switching. The personality that has taken control of the body is said to have fronted.

The person suffering from Multiple Personality Disorder often has little or no control over this switching and which particular alter fronts. The switching usually happens as a response to stress, fear or anxiety.

When the host comes back, so to speak, they often report that they can’t remember what happened to them while an alter had taken over their body.

People with Multiple Personality Disorder are initially unaware of their condition and their alters. The amnesia or memory gaps that they experience after switching are among the first signs of the disorder that they notice.

They’ll end up at a certain place and not remember how they got there. They’ll lose track of time and sometimes others will tell them that they did things they don’t remember doing.

What causes Multiple Personality Disorder?

Multiple Personality Disorder is the mind’s response to severe and prolonged trauma, especially in early childhood. In my post regarding dissociation, I mentioned that the mind dissociates to allow the victim of a traumatic experience to bear the trauma.

Multiple Personality Disorder is one severe case of such dissociation. Instead of simply disconnecting from the traumatic experience, the victim creates alternate personalities who can bear the trauma and deal with it while the host forgets about it. (Take this test to assess your risk of a dissociative disorder).

While it’s usually continued physical and sexual abuse that causes Multiple Personality Disorder, it may also be caused by emotional abuse in early childhood.1 

Traumatic experiences in adulthood such as wars and natural disasters can also cause Multiple Personality Disorder. Moreover, some psychoactive drugs produce the same symptoms so before diagnosing someone with the condition, clinicians make sure that substance use is not a factor.2

Some researchers have suggested that MPD is iatrogenic, meaning that the condition is induced in the patient during therapy. They noted that a disproportionate number of diagnoses were made by a small number of clinicians.

It was argued that the condition was caused by therapists hinting to patients that their unpredictable behaviors were caused by alternate personalities. This, in turn, led the patients to create these personalities.3

What exactly causes Multiple Personality Disorder is a topic of debate because different people can respond differently to trauma. However, it’s worth noting that around 99 percent of individuals with the condition have reported recurring, life-threatening and overpowering disturbances in their lives before the age of 9.

The idea that mere suggestion by therapists can cause such an extreme phenomenon in patients as splitting of their personality seems far-fetched.

How alters behave in Multiple Personality Disorder

The behavior of alters provides a clue to understanding the connection between MPD and trauma. If we go by the traumagenic theory, we should expect alters to be more equipped to deal with trauma or stress. This is often the case

For instance, a person who is emotionally weak tends to have an alter who is emotionally strong. A person who is passive and meek tends to have an alter who is active and aggressive.

When people with Multiple Personality Disorder encounter a stressful situation or if something reminds them of their past trauma, they often switch to an alter better equipped to deal with the situation.

In this sense, this condition can be adaptive rather than maladaptive. Were it not for these better-disposed alters, the host may not have been capable of coping with such situations. 

However, the story of Multiple Personality Disorder is not all that rosy. There are also alters that are prone to self-harm and may even lead the person to commit suicide.

These are often alters who remember each and every detail of the trauma, so consumed by shame and self-destructive thoughts that they carry out acts of self-harm and contemplate suicide.

This is why people with this condition tend to be highly suicidal. Contrary to what the media often portrays, people with Multiple Personality Disorder are more likely to harm themselves than others.

multiple personality disorder movie
Movies about Multiple Personality Disorder are always fun, despite their overemphasis on violence.

If the host has good relations with the alters, the chances of self-harm and suicide seem to decrease. People with Multiple Personality Disorder often communicate with their alters via journaling (alters have different handwritings). Others can do it in their heads. They are co-conscious with their alters. When an alter fronts they can observe what’s going on and what the alter is doing without zoning out. 

Therapy can boost communication among alters and allow the patient’s different personalities to come to terms with the trauma, fostering a harmonious relationship among the alters and, ultimately integrating the personalities.4 Some patients, however, refuse integration because they feel too attached to their alters.

We all have multiple personalities

We all have Multiple Personality Disorder in its most basic, rudimentary form. Talking to oneself would’ve made no sense if our self wasn’t divided into a speaker and a listener.

Can a single self both talk and listen to itself? If you’ve ever engaged in journaling, you may have observed that when you reflect on your life you talk as if you’re talking to someone else in your head. 

Look at the following journal entry by Rob, for example:

Had a fight with wife today. Why does this keep happening to you Rob? Is it you or is it her? Come on Rob! You’re better than this. I know you can bring things back to how they were before.

It’s perfectly normal to refer to yourself from the vantage of someone else in your head because it makes our behaviour objective, helps us solve our problems and navigate through life.

It’s possible that in people with Multiple Personality Disorder this little voice that is present in all of us has turned into a whole another personality, or personalities rather.

By the time we’re adults, almost all of us develop a strong sense of our identity, a sense of who we are. This identity is comprised of multiple identities that are often stolen from other people (often celebrities because they tend to have desirable identities).

These identities are more or less coping mechanisms that we develop to deal with stressful situations and our life problems.

Say a part of your identity is, “I’m an assertive person”. At some point in your life, you probably were not an assertive person. By looking at how assertive people behave, you integrated this identity into your personality. So next time you needed to be assertive, this assertive person inside of you took control.

This assertive person might be your friend, a neighbor, a co-worker, or a celebrity that you admire for their assertiveness. You feel yourself becoming them in the moment and act as if they would. It’s almost as if that person temporarily possesses you. 

The difference between this phenomenon and the phenomenon of Multiple Personality Disorder is that in the latter, these identities that people make a part of their personalities become full-blown separate people.

While normal people are able to maintain a coherent self through all of their different identities, people with Multiple Personality Disorder lose this ability. 

When therapists try to convince people with Multiple Personality Disorder that all of their different personalities are, in fact, them, they’re trying to rebuild this sense of coherent self that was disintegrated in response to trauma.


  1. Ross, C. A., Norton, G. R., & Wozney, K. (1989). Multiple personality disorder: An analysis of 236 cases. The Canadian Journal of Psychiatry34(5), 413-418.
  2. Ross, C. A. (1997). Dissociative identity disorder: Diagnosis, clinical features, and treatment of multiple personality. John Wiley & Sons Inc.
  3. Lynn, S. J., Lilienfeld, S. O., Merckelbach, H., Giesbrecht, T., & van der Kloet, D. (2012). Dissociation and dissociative disorders: challenging conventional wisdom. Current Directions in Psychological Science21(1), 48-53.
  4. Fine, C. G. (1999). The tactical-integration model for the treatment of dissociative identity disorder and allied dissociative disorders. American Journal of Psychotherapy53(3), 361-376.