Louisa Degenhardt, Wayne Hall and Michael Lynskey, “Testing hypotheses about the relationship between cannabis use and psychosis,” Drug and Alcohol Dependence 71, issue 1 (July 20, 2003): 37-48.

The relationship between marijuana use and psychosis is a subject of ongoing controversy. In this study, a respected group of Australian researchers took the data on marijuana use rates and rates of schizophrenia and ran a series of computer models to test the possibilities that marijuana: a) causes schizophrenia, b) precipitates schizophrenia in vulnerable persons, c) aggravates schizophrenia in people who already have it, or d) that schizophrenics are more likely to use marijuana (i.e. that marijuana use is the effect, not the cause, of schizophrenia). Their conclusion: Greatly increased rates of marijuana use were not accompanied by increased rates of schizophrenia. Marijuana does not appear to cause schizophrenia, but may aggravate it or precipitate it in vulnerable persons.

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