I've known a lot of people that smoke marijuana and just like any other drug some people should not take it. My sister was diagnosed with schizophrenia and she is the last person you would want to smoke a joint. She has had enough sense not to. Her problem is cigarettes. My husband was on a high dose of Seroquel (300mg) and he could handle it but my doctor tried me on a 25mg dose to start and I will never take that again. It did some strange things to my head. Same with Lithium, I take 300mg. with no problem but it would make him sleep all day. My husband smoked to ease his anxiety, and to help him with his physical pain. He would be calmer, happier, and would feel like moving around doing things. We were both diagnosed as Bipolar.
I believe that my Sza was triggered by marijuana use. The 1st time I heard voices was when I was high. I became paranoid and delusional. The last time I got high, 24 years ago, I was totally out of it. My pdoc said that my Sza was always there, but the drugs brought it out. I believe even if I didn't do drugs I would still have gotten sick. It may have been later in my life, but it was and is always in me.