system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is happening in the brain when someone has dissociative identity disorder (split personality)?  Does each personality get a portion of the brain/mind?  What happens during the switch of personalities?

* Why do the personalities switch? 
* What causes the change? 
* Does each portion make their decisions, or is it a group effort? 
* Are both personalities active all the time?
* Is it possible to have several different personalities?
gpt
There is still serious debate in the psychological community whether dissociative identity disorder truly exists.

It is almost exclusively a North American phenomenon, with limited diagnoses in Europe and almost none in Asia.

Given the fact that many psychologists don't even believe the disorder exists, it is difficult to speak to its precise mechanisms.