Comment by kayodelycaon

From what I've read of schizophrenia[1] it is highly inherited and unlikely that any drug would cause it. A sufficient amount of stress is known to trigger or quicken the emergence of schizophrenia in people already predisposed to it.

When it comes to studying this, you have to separate out:

* The high rates of drug abuse by people with mental illness.

* The correlation drug use with other sources of stress. Drug use may not be the source, but a result of the source. (But I think we can all agree drugs probably aren't happening matters.)

* Misdiagnosis of temporary drug-induced psychosis as a permanent, incurable mental health illness.

* Race, sex, age, and location, since this all affect the normal rates of schizophrenia for each population group.

OR:

* Show a significant increases in rates that can't be explained by the above. (If this rate tripled, it's pretty clear something bad is happening.)

Very few studies do this, because it is very difficult and there is little incentive to do high quality research.

1: I'm bipolar which is sometimes considered to be on the same spectrum