>earlier diagnosis of psychosis/schizophrenia

Emphasis mine. This seems interesting to me. Earlier diagnosis is not more diagnosis. It could just mean that due to illegality, these people got into contact with mental health professionals earlier than they would have otherwise. Also getting the diagnosis earlier. But not being more schizophrenic.

I'm generally pro-legalization, but if marijuana is shown to make people schizophrenic who would otherwise not become schizophrenic, it's a big deal. It has severely affected their lives and those around them. Tobacco doesn't give everyone lung cancer after all, some are more at-risk than others. Quantitatively determining that risk, doing cost-benefit, etc, is important, but I don't think this should be dismissed out of hand as immaterial.

Yes that would be a big deal but that's not what the evidence is saying.