So if there's a normal rate of substance abuse in any given population... Let's for shits and giggles say that 1% of all people have some form of substance abuse problems...

But schizophrenic people are more susceptible to it substance abuse increasing their volatility/making them more violent than the normal population of substance abusers... How is this not a schizophrenic-based problem? It should be even more predominant because the population of Schizophrenic people vs normal population that needs to be medicated (unlike the general population at large)...

Edit: for clarity

Schizophrenic population has greater rates of substance use due to medications. Schizophrenic populations are less favorable by genetics to react to medications.

These two facts (supported by previous study linked), mean that the population is more risky for the behavior. Regardless is the Schizophrenia itself not being the direct problem... it's certainly a meaningful contributor.