Pot is one of those drugs that appears to maintain a fairly good rep, despite its growing bad rep. Consider this research that will be published this June in the Archives of General Psychiatry.
This particular study found that marijuana use is associated with early development of psychosis. Scientists analyzed 83 studies involving over 8,000 subjects who used pot and over 14,000 subjects who did not. They compared the age of onset for psychosis between these groups. And they found that those who used cannabis developed psychosis nearly three years younger than those who did not use any pot.
The researchers proposed some theories behind the pattern. One that cannabis use is a causal factor for schizophrenia, or that it precipitates psychosis in vulnerable people. They also theorize that cannabis might simply exacerbate symptoms of schizophrenia. Or the link could come from the other direction of course, those suffering from schizophrenia may be more likely to use pot.
The evidence here suggests that limiting marijuana use could delay or even prevent some cases of psychosis. And timing is important, since earlier onset of schizophrenia is linked to a worse prognosis overall.