Daily use of high-potency cannabis is associated with more positive symptoms and fewer negative symptoms in first-episode psychosis patients. Among 901 patients and 1,235 controls across six European countries, those who used high-potency cannabis daily had the highest scores on positive symptoms, while negative symptoms were more common in patients who never used cannabis. Psychotic experiences in controls were linked to current cannabis use but not to lifetime use. Depressive symptoms showed no differences related to cannabis use in either group.
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.
Cannabis consumption is not associated with increased inflammation in first-episode psychosis patients or controls, indicating that inflammation does not mediate the cannabis-psychosis link. However, daily cannabis use and onset of use before age 17 interact with a composite measure of systemic inflammation to raise the odds of psychosis beyond the individual effects of either factor alone, and this association appears only among individuals with medium-to-high inflammatory scores. The authors propose that immune dysregulation may modify the cannabis-psychosis relationship, consistent with a two-hit hypothesis, and that immune dysregulation could be part of psychosis pathophysiology independent of cannabis use or other confounders.