Cannabis use and psychosis: a review of clinical and epidemiological evidence.
The Australian and New Zealand journal of psychiatry February 1, 2000 W Hall, L Degenhardt
This review examines two hypotheses linking cannabis use to psychosis. The first, that heavy cannabis use can cause a distinct 'cannabis psychosis' that would not otherwise occur, has limited clinical support; such cases appear rare and likely require very high tetrahydrocannabinol doses, prolonged use of potent cannabis, or a preexisting vulnerability. The second hypothesis, that cannabis use may precipitate or worsen schizophrenia, has more backing: one large prospective study found a linear relationship between cannabis use frequency by age 18 and schizophrenia diagnosis risk over 15 years. However, it remains unclear whether cannabis precipitates schizophrenia, represents self-medication, or if other drug use explains the association. Cannabis use can exacerbate schizophrenia symptoms.