In conclusion, we found that polygenic liability for schizophrenia was associated with an increased risk of cannabis-related paranoia, depression and anhedonia, decreased social contact, and cognitive difficulties, even when accounting for the effects of other pertinent risk factors including CUD, age at first use of cannabis, and lifetime use of other illicit substances. As noted above, our findings come from ascertained samples with a high prevalence of CUD and use of other substances; thus, it is unclear whether these findings will generalize to population-based samples. Our results support the hypothesis that individuals who have a preexisting genetic vulnerability for schizophrenia are more likely to report unusual experiences, especially cognitive difficulties, when using cannabis.
