My understanding is cannabis can trigger schizophrenia in those with a predisposition. Some people will have this triggered in their lifetime, and others will not. Some things like stress can trigger this, as well as some drugs like cannabis
Also it's known(both by researchers and users) that cannabis can increase/create paranoia in some people. And paranoia is stressful so that can lead to schizophrenia(and paranoia is a part of the diagnostic criteria for schizophrenia).
