It's unpredictable, even if you think you can adjust for mental illness in your family. I got a bunch of undiagnosed Asperger's type stuff in mine and a formerly progressive schizophrenic uncle (medicated now). I never really had big problems, hear voices or anything. I have high functioning autism (semi mild form) myself, but have only been pseudo psychotic induced very temporarily by big amounts of drugs. All things considered I count myself lucky and resilient.
Problems are:
- It is hard to judge yourself. A lot of people with latent mental illness don't notice much wrong with them. And especially schizophrenics will try to explain their problems in backwards explanations.
- It is determined by genes and even with a known family history it is a crapshoot of probabilities.
That said, if you have schizophrenia presented in one of your direct ancestors your probabilities unfortunately go up quite a bit. Perhaps something can be said from how many of the descendants also show the trait.
There is a form of sensitivity that makes some people incredibly susceptible to psychosis from cannabis use and this can actually be tested genetically. But even besides that there are other factors, like starting at a young age will increase your risks manifold, also the more chronic use is - I think - the more hazy things can get.
If you feel sober and stable in your thoughts, not easily influenced by suggestion... or quite the opposite, that is an indication. Same for your ability to keep deep thought / ideation / fantasy and 'confirmed' or consensus reality apart.
It can boil down to how you react to losing control and losing track of your senses. If you cope even going loosy goosey, that helps... but if you tilt at the least perplexion that does not help.
Psychosis is also associated with ontological insecurity. That means that some people define themselves very strongly in terms of being acknowledged by others. That is a huge risk... it is necessary to be used to 'feeling yourself / your self' in order to ease up on that. If you hang on tightly or by a thread to begin with, much less is necessary to push you over the edge. For some I guess it is truly inevitable, since life will always throw you a curveball on occasion.
Start very very low if at all, and check your reaction. If nothing much happens or if it is a success, still only increase the dose a little (from the same batch! always start low with every new batch!!), don't just double it casually.
It takes getting used to for pretty much everyone, a trip is pretty extraordinary, but at the first sign of worrisome instability, stop.
Best is to have benzos and antipsychotics on hand and a tripsitter.