Science

I'm not sure that finding out by having an episode triggered that results in hospitalization is a good thing.

The earlier its diagnosed, the more severe it tends to be. If someone has schizophrenia triggered under the age of 25, the massive shift in the balance of neurotransmitters has a significant effect on the continuing development of the brain. The frontal cortex (the executive function, intelligence/wisdom, and common sense part of the brain) is the last part to finish developing. That's why you can have teenagers and college-aged kids that are extremely smart academically, but absolute morons when it comes to decision making and self-restraint.

Schizophrenia is characterized by massive overloading of dopamine to the point that the brain malfunctions, and the medications used to treat it (anti-psychotics) mostly work by dulling the effects of dopamine and limiting its production. Finding the right anti-psychotic and right dose of that drug can take a lot of trial and error, and that's all time lost for ongoing development of that person's brain. Dopamine is a very important neurotransmitter, so if someone has severe schizophrenia requiring strong dopamine inhibition, they can end up with a lot of nasty side effects.

The medications have long term effects too and there's kind of a maximum amount of time you can be on an anti-psychotic before you start having a form of medication-induced Parkinsonism. If someone's schizophrenia gets triggered then diagnosed and treated earlier, it means they are going to start having those Parkinson's symptoms that much earlier.

I work in medicine (mostly emergency medicine), and I have seen a lot of people end up with their lives completely torn apart because of permanent effects of psychotropic drugs. CBD has a lot of benefits and some real clinical evidence backing it up, but there really aren't any non-recreational uses for THC and the people who want to use marijuana for calming effects can get CBD on its own these days.

Given that, as a species, we have only just recently figured out how to diagnose any of these things, it is highly unlikely that these conditions are nowhere in your family lineage. There is always the possibility of de novo mutations that can shake things up, but people with schizophrenia used to just be called generically insane...or they were prophets or cult leaders if they rolled high on Charisma.

You'd have differ between public harm and self harm. Also you miss the point, both can be bad in different ways. The links of THC use under 25 leading to psychosis and trigger/cause early onset of schizophrenia are more than established. I won't choose between liver cirrhosis and mental health problems because both ruin your life. You don't need organ failure rot in a clinic or become homeless with schizophrenia and off yourself. I've seen both substances ruin lives and my country of residence has infinitely better, and free, mental health care.