In my fourth year of my PhD on schizophrenia and I'm currently writing up my thesis. I'm procrastinating right now so thought I'd do something useful with what I've been studying.
And no, schizophrenia is not multiple personality disorder.
Edit: I have to get dinner and run some errands. I'm really enjoying this so I will definitely get back and answer the rest of the questions.
There is a genetic component to it but it's unclear how it's triggered. There is no "schizophrenia" gene like Huntington's. I think the commonly known triggers include stuff like trauma or extreme stress.