Childhood adversity and cannabis use are both known risk factors for psychosis. This study examined whether cannabis use might explain the link between childhood adversity and psychotic disorders. Data from 881 first-episode psychosis patients and 1231 controls from the EU-GEI study showed that household discord was associated with psychosis partly through cannabis use. Lifetime cannabis use mediated 17% of the association, cannabis potency mediated 14%, and frequency of use mediated 29%. Similar results appeared for early exposure to household discord. The findings suggest that harmful cannabis use patterns partially explain how household discord leads to psychosis, and children exposed to challenging home environments could benefit from interventions to prevent cannabis misuse.
Exposure to cannabis increases the risk for psychoses ranging from transient psychotic states to chronic recurrent psychosis. Greater dose and earlier age of exposure raise the risk. For some psychosis outcomes, evidence supports some causality criteria, but reverse causality and confounders cannot be ruled out. Cannabis is neither necessary nor sufficient to cause psychosis; it is likely one of multiple causal components. In those with established psychosis, cannabis negatively affects the illness course and expression. Emerging evidence suggests alterations in the endocannabinoid system in psychotic disorders. Delaying or eliminating cannabis exposure could potentially reduce psychosis rates, especially in high-risk individuals.