Cannabis-induced psychosis: a cross-sectional comparison with acute schizophrenia.

OBJECTIVE The existence of cannabis-induced psychosis (CP) remains controversial, partly because of methodological problems. We hypothesize that acute schizophrenia (AS) and CP can have distinct demographic, premorbid and clinical features. METHOD We compared 26 patients with CP to 35 with AS, after their cannabis-consumption status was confirmed by repeated urine screens. Patients with CP were assessed after at least 1 week but not more than 1 month of abstinence. Symptoms were evaluated with the Present State Examination (PSE). RESULTS In group CP, male gender, expansive mood and ideation, derealization/depersonalization, visual hallucinations, and disturbances of sensorium were more frequent than in group AS. Premorbid schizoid personality traits were more frequently associated to AS and antisocial personality traits to CP. CONCLUSION The continuous heavy use of cannabis can induce a psychotic disorder distinct from AS. These two clinical entities share some features but they differ in others.