Dissociative Identity Disorder is one of the four main kinds of dissociative disorders (Kaplan, 1998). The main feature of Dissociative Identity Disorder is a disturbance in identity that involves two or more personalities taking control of the body. DID used to known as Multiple Personality Disorder (MPD). This disorder has been of great interest in the field of psychology. About 1% of the general population is diagnosed with Dissociative Identity Disorder but it is possible that up to 7% may have undiagnosed dissociative disorder. 

The following are excerpts from an interview done with a woman who has Dissociative Identity Disorder:

"It’s a survival mechanism so that when, as a young child, you're abused or suffer severe trauma you actually dissociate so you have a type of out of body experience. And then if it’s consistent then that out of body experience becomes a mini personality. And they take all the pain and the emotions that you / me, the individual, would be suffering. Then as abuse continued through different ages then I developed different personalities, or they’re part personalities, to take away the pain at different times. So as the abuse continued over quite a long period of time, I developed different alters, different personalities to take different parts of the pain and experiences from me."

"They’re me at different ages. So the six year old is there to take away particular pain and abuse and, yes, I hear a sort of constant talking, chattering in my head so they’re auditory hallucinations, but I know they’re not real... I know they’re me they’re not external voices talking to me. And yes I can see them. Some of them I can see as clearly as I see everything else around me."

"I can remember moving to my side and actually looking at myself being abused, so you’re like an onlooker. People who’ve had near death experiences or serious car crashes talk about out of body experiences and I can remember that happening then. And it’s probable that it wasn’t the first time because at that time I saw two others as well that were much younger. So I’m assuming that I had alters before that, but I can’t be certain." 

The whole interview can be found at http://www.bbc.co.uk/ouch/interviews/ruth_dee.shtml