....students often ask me whether multiple personality disorder (MPD) really exists. I usually reply that the symptoms attributed to it are as genuine as hysterical paralysis and seizures....--Dr. Paul McHugh.
MPD(multiple personality disorder) or DID(dissociative identity disorder)is a psychological term used to describe the state of mind where a person shows "altered" behaviour and presents themselves as a different person. A person with MPD plays host to two or more personalities (called alters). The "alters" are said to occur spontaneously and involuntarily, and function more or less independently of each other. Each alter has its own unique style of viewing and understanding the world and may have its own name. These distinct personalities periodically control that person's behavior as if several people were alternately sharing the same body. The unity of consciousness, by which we identify our selves, is said to be absent in MPD. Another symptom of MPD is significant amnesia which can't be explained by ordinary forgetfulness.
MPD occurs about eight times more frequently in women than in men. Furthermore, Female MPD patients often have more identities than men, averaging fifteen as opposed to eight for males.
Causes:-
Most people diagnosed with MPD were either physically or sexually abused as children. Many times when a young child is severely abused, he or she becomes so detached from reality that what is happening may seem more like a movie or television show than real life. This self-hypnotic state, called disassociation, is a defense mechanism that protects the child from feeling overwhelmingly intense emotions. Disassociation blocks off these thoughts and emotions so that the child is unaware of them. These thoughts and actions are mainly controlled by the subconsious part of human brain whic retains information facts that the consious mids fails to observe and remember. In effect, they become secrets, even from the child. According to the American Psychiatric Association, many MPD patients cannot remember much of their childhoods.
Not all Children who are severely and repeatedly abused develop multiple personality disorder. However, if the abuse is repeatedly extreme and the child does not have enough time to recover emotionally, the disassociated thoughts and feelings may begin to take on lives of their own. Each cluster of thoughts tends to have a common emotional theme such as anger, sadness, or fear. Eventually, these clusters develop into full-blown personalities, each with its own memory and characteristics.
Symptoms:-
A person diagnosed with MPD can have as many as a hundred or as few as two separate personalities. (About half of the recently reported cases have ten or fewer.) These different identities can resemble the normal personality of the person or they may take on that of a different age, sex, or race. Each alter can have its own posture, set of gestures, and hair-style, as well as a distinct way of dressing and talking. Some may speak in foreign languages or with an accent. Sometimes alters are not human, but are animals or imaginary creatures.
The process by which one of these personalities reveals itself and controls behavior is called switching. Most of the time the change is sudden and takes only seconds. Sometimes it can take hours or days. Switching is often triggered by something that happens in the patient's environment, but personalities can also come out under hypnosis (a trancelike state in which a person becomes very responsive to suggestions of others).
Despite of all, it has been found that through regular medication and therapy a link can be created between the alters though it can't be compleately irradicated. With aging the frequency of switching slows down. During the therapy the therapist tries to isolate each personality and address their emotional issues regarding the original trauma. Sometimes mood alteration medicines such as tranquilizers and antidepressants are prescribed. This medication can last upto an average of 4 years.
For further reading:
http://www.hypnosis-nlp-therapy.com/subconscious.html
http://www.mental-disorder.net/wb/pages/personality-disorders/multiple-personality-disorder/causes-of-multiple-personality-disorder.php