ORIGINAL ARTICLE Familial Predisposition for Psychiatric Disorder Comparison of Subjects Treated for Cannabis-Induced Psychosis and Schizophrenia

Context: Cannabis-induced psychosis is considered a distinct clinical entity in the existing psychiatric diag-nostic systems. However, the validity of the diagnosis is uncertain. Objectives: To establish rate ratios of developing can-nabis-induced psychosis associated with predisposition to psychosis and other psychiatric disorders in a first-degree relative and to compare them with the corre-sponding rate ratios for developing schizophrenia spec-trum disorders. Design: A population-based cohort was retrieved from the Danish Psychiatric Central Register and linked with the Danish Civil Registration System. History of treat-ment of psychiatric disorder in familymembers was used as an indicator of predisposition to psychiatric disorder. Rate ratios of cannabis-induced psychosis and schizo-phrenia associatedwith predisposition to psychiatric dis-orders were compared using competing risk analyses. Setting:Nationwide population-based sample of all in-dividuals born in Denmark between January 1,1955, an