Ok, this bugs the tar out of me, especially since I’ve seen a _lot_ of writers, both for books and for TV, who get this wrong. Schizophrenia is _NOT_ the same thing as multiple personalities. Schizophrenia involves delusions and hallucinations, among other things (see _A Beautiful Mind_ for a flick that actually gets it right). Dissociative Identity Disorder (formerly known as Multiple Personality Disorder before the DSM-IV revision) is what is _actually_ multiple, or split, personalities. It’s a common misconception that the two mental disorders are one and the same. Stephen King got it wrong in _The Dark Tower_ series (and should, in my opinion, have fixed it in Book 5, given the timespan between it and Book 4), and the writers of _Stargate SG-1_ got it wrong in a couple of episodes, just to name two examples. There have been plenty of others I’ve seen lately, too.
Get it right, people!
(Aren’t writers supposed to do research on these things?)