A lot of people who do drugs are actually - like a lot of alcoholics - “self medicating.” Alcoholics do it for depression (although it doesn’t help) and other drug users are trying to deal with other problems.
But just as excess alcohol actually makes depressed people more depressed ultimately, “recreational” (that is, mood altering) drugs make psychotics even worse.
Pot, which many people want to legalize, is actually one of the worst because the reaction is not acute but cumulative, with the result that the habitual stoner gradually changes...with paranoia being one of the results. Believe me, I’ve seen this first hand.
In the case of somebody who is already a schizophrenic and is self-medicating this can be a disaster, as we have seen.
Make drugs legal and we will see a lot more Jared Loughners