There is a book about multiple personality disorder writtan by a person who has the problem. It it "When Rabbit Howls" by the troops for Truddi Chase. It is an excellent description of the problen and may lead to valuable insights.

I think the reason it does not get diagnosed in children more frequently is because children who have it have a personality that always shows up in the presence of medical personnel, so no medical person would observe it because the child always is consistent around them. It's only when you observe over a long period of time in various situations that the truth comes out.

And no, they are not demons. They are fragments of a whole personality that arise to deal with specific issues and abusers. The real demons are in the ones who perpetrated the child abuse in the first place. They are truly demon possessed, in my humble opinion.