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Understanding the Causes of Multiple Personality Disorder

written by: Terrie Schultz • edited by: Paul Arnold • updated: 3/11/2011

Sometimes referred to as “split personality,” multiple personality disorder is a condition in which a person’s consciousness has dissociated into two or more separate personalities. The causes of multiple personality disorder are thought to be physical, sexual or emotional abuse in childhood.

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    What is Multiple Personality Disorder?

    Multiple personality disorder, also known as dissociative identity disorder, is a condition in which an individual has two or more distinct personalities, known as alters or alter egos. The different personalities are unique and each has its own name, identity and characteristics. Each of these personalities is in control of the individual’s thoughts and actions at different times. The alters may or may not be aware of each others’ existence, and while one of the personalities is in charge, the other personalities may experience it as a lapse of memory.

    Statistically, multiple personality disorder occurs in an estimated 1% of the population, and up to 7% may have had an undiagnosed dissociative disorder at some time in their life. In adults, it is nine times more likely to occur in females than in males, but in children there are approximately equal numbers of boys and girls with the disorder. The reason for this difference is not known.

    Multiple personality disorder usually occurs in conjunction with one or more other disorders, including post traumatic stress disorder, borderline personality disorder, and conversion disorder.

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    Causes of Multiple Personality Disorder

    The majority of individuals diagnosed with multiple personality disorder were physically or sexually abused as children, usually before the age of nine. It is thought that multiple personality disorder develops as a result of physical or emotional trauma suffered during childhood. Development of multiple personality disorder is more likely if the abuse is repeated frequently, so that the child is unable to recover from each episode of abuse before another occurs, and also if there is no caring or sympathetic person in the child’s life to provide comfort.

    The victim of abuse may react by dissociating or detaching from the experience. Detachment is a defense mechanism that causes a disturbing or painful experience to seem unreal, as though watching it on television or seeing a movie. The intensely negative feelings and memories associated with the abuse may become compartmentalized and sequestered in the child’s mind so that these memories are no longer accessible to his primary identity. Over time, these clusters of emotions, thoughts and memories may eventually develop into separate personalities with distinctive characteristics. Individuals with multiple personality disorder are often unable to remember their childhoods very well.

    Whether or not an individual develops multiple personality disorder may also be influenced by brain chemistry. Large numbers of neurochemicals are released in response to trauma, and these neurochemicals have an effect on how memories are stored and accessed. Some people may be more prone to dissociation than others, and when their brain is flooded with these neurochemicals in response to a traumatic experience, it causes their memory to become fragmented or compartmentalized.

    Other causes of multiple personality disorder may be entirely physiological, such as temporal lobe epilepsy, Alzheimer’s disease, stroke, or encephalitis. There may be a genetic factor, because the probability of developing multiple personality disorder is slightly higher for those with a family history of the disorder.