Frankly if you have serious mental health issues you should probably avoid cannabis altogether.
I'm of the opinion that "treating" mental illnesses with marijuana is a myth (note: not all of them). Treating depression and anxiety by smoking is a crutch, not a treatment. I'm speaking from experience on this one (clinical depression and GAD, ranging from quite mild to moderately severe depending on how my life is going at a given time).
I learned quickly that consuming large amounts of cannabis in a sitting was not the way to go for me as it would cause paranoia and worsen my anxiety, especially on the social side. So I took to microdosing and vaping, which worked GREAT. I'd vape a .1-.2 bowl and feel fantastic, no inhibitions about socializing, happier, etc. So I kept doing it.
However, a little ways down the road, I started noticing that when I was sober, I was having trouble focusing, much more irritable, generally down, and far more anxious than normal, so I would always be going to smoke and trying to maintain my high.
THIS IS NOT TREATING A MENTAL ILLNESS! I was smoking because the altered state of mind felt better, but if it makes me worse when I'm sober, than how the fuck am I actually treating it? (Answer: I'm not, I'm hiding from it) I could be stoned all the time, but why would I want to spend a huge portion of my income to do so rather than finding other ways to cope?
Especially in the case of schizophrenia or psychosis you should REALLLLYYYY avoid weed man. That's getting yourself into dangerous territory when you're consuming with regularity.
I'd also like to make it clear that I still smoke regularly, but that was AFTER I sat down and addressed my mental health issues and got my life to a point where I was happy, and as soon as I notice my depression worsen I immediately cease consumption nowadays.