Question  Are substance use disorders, in particular cannabis use disorders, associated with conversion from schizotypal disorder to schizophrenia? Findings  In this Danish nationwide, register-based cohort study that identified 2539 participants with incident schizotypal disorder, any substance use disorder was associated with conversion to schizophrenia at a rate of 33.1%; for cannabis use disorders, the conversion rate was 58.2%. Results were statistically significant after controlling for confounders. Meaning  Universal and substance-targeted prevention efforts are needed to reduce conversion to schizophrenia in individuals with schizotypal disorder.. Please contact the library to request a copy of this article - http://bit.ly/1Xyazai