Esther Inglis-Arkell explores the history of the condition:
The powerful multiple personality disorder has been humbled and dismantled into four "dissociative disorders," each comprising part of the original idea. Dissociative amnesia is memory loss, especially of a traumatic event from childhood. Dissociative fugue is what happens when someone walks away, semi-deliberately, from their life and lives under a new identity for a few hours or a few months. The end of the fugue can bring on anything from complete lack of memory to "feeling out of sorts."
Depersonalization disorder is the classic state of "watching life like it's a movie," and may come with a skewed perception of time and space. And finally there's dissociative identity disorder, which is characterized by switching between different personalities with different histories, mannerisms, and physicalities. Although this may be associated with dissociative amnesia, it's often more gentle than that. Often people feel a sense of multiple people living in their heads at once, and feel a sense of fragmentation between personalities, not complete divides.
That's if anyone believes it happens at all. Many psychiatrists think that this is a cultural behavior rather than a mental one.
The Dish 