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.
For some drugs, its possible to trigger psychotic episodes (such as from meth, lsd etc.). Whether or not you can trigger schizophrenia, there is some evidence that those who have a genetic inclination have "triggered" it from smoking pot. It's quite rare, and the mechanics behind it aren't really known. To be honest, the main thing I learnt about schizophrenia from doing the PhD is that "we don't know shit about schizphrenia" haha.
A family member supposedly had this (On the other hand he was a lawyer working 22 hour days and was smoking pot full time because he was in the early stages of having a nervous breakdown, so not exactly a non-confounded test case.)
That said, pot has an immediate and very bad effect on me so I stay the hell away from it and just try to locate where the ecstasy is, so maybe there is something to the genetic disposition.
Yea, that doesn't sound like a good recipe for mental health. I avoid pot too, after having a particularly bad experience a couple of years ago. Wasn't really psychotic, but my entire body started getting weird sensations and half my field of vision turned red. I can't smoke without experiencing anxiety now, so I've just stopped.