Cannabis use and onset of mental illness
Several studies had suggested and a recent meta-analysis (1) further concluded a significant effect of cannabis use on the age of onset of psychotic illness. The meta-analysis found that the use of cannabis as well as use illicit substances in general, was associated with an earlier age at onset of schizophrenia and psychotic disorders. In contrast, alcohol use alone did not appear to be significantly associated with a younger age at onset of psychosis. The illness was found to have its onset 2.7 years earlier in the case of cannabis use, and 2 years earlier in general substance use populations.
N-acetylcysteine 1200mg BID was effective in reducing cannabis use in adolescents (Gray KM Am.J.Psychiatry 2012). Recent attempt to replicate in adults was not effective. Naloxone was not found to be effective in helping with cannabis use.
(1) Large M et al. Cannabis Use and Earlier Onset of Psychosis: A Systematic Meta-analysis. Arch Gen Psychiatry. 2011