Does cannabis cause psychosis or schizophrenia?

Cannabis use is associated with increased risk of psychosis, but the relationship is complex and not simply causal. Key findings: (1) Meta-analyses find cannabis users have ~2x increased risk of psychotic disorders vs. non-users; daily high-potency (>10% THC) users have ~5x risk. (2) The association is dose-dependent — frequency, potency, and age of onset all matter. (3) Genetic vulnerability is critical — individuals with COMT Val158Met polymorphism or family history of psychosis are at substantially higher risk. (4) CBD appears to counteract THC-induced psychotomimetic effects — high-CBD strains are associated with lower psychosis risk than high-THC strains. (5) Causality vs. self-medication: some individuals with prodromal psychosis use cannabis to manage symptoms, inflating the association. The current scientific consensus (including NIDA and WHO) is that cannabis can precipitate psychosis in genetically vulnerable individuals and worsen outcomes in those with established schizophrenia, but does not cause schizophrenia in the general population.