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.
First-episode psychosis patients who also have cannabis use disorder show more severe positive symptoms, dissociative experiences, and worse overall functioning compared with patients who do not use cannabis, even when both groups receive comparable antipsychotic treatment. Over an eight-month follow-up, cannabis users continue to have higher levels of positive symptoms and dissociation, and their global functioning worsens, while functioning improves in non-users. The findings suggest that greater dissociation and positive symptoms at first episode and their persistence may characterize cannabis-associated psychosis and help explain the diverging trajectories in functioning.