Cannabis use and attenuated positive psychotic symptoms: A multiple mediation model

Abstract

Cannabis use has been associated with various psychosis outcomes, including psychotic disorders, the clinical high risk period of psychosis, and subthreshold measures of psychotic symptoms in non-clinical samples, such as attenuated positive psychotic symptoms (APPS). The present study examined whether individual- and contextual-level factors account for the relationship between cannabis use and psychosis. Specifically, we hypothesized that the relationship between cannabis and psychosis would be mediated by social functioning; negative, depression, anxiety, and aggression symptoms; context of cannabis use; and motivations for cannabis use. Nine hundred and forty-five young adults ages 18-35 years (M = 20.1 years, 24.4% male) completed self-report questionnaires: the Prodromal Questionnaire, Marijuana Use Form, Social Functioning Scale, Center for Epidemiologic Studies Depression Scale, State-Trait Anxiety Inventory-Trait Form-Anxiety Subscale, Social Phobia Scale, Life History of Aggression Scale, Reasons for Use scale, and Drug Use Frequency questionnaire. Psychosis outcomes included a dimensional measure of APPS and a dichotomous measure indicating potential higher/lower risk for psychosis, based on number of distressing symptoms endorsed (i.e., D-APPS status). A multiple mediation framework was used, and significance of mediators was evaluated through estimating the significance of indirect effects using bootstrapped confidence intervals. Increases in negative and aggression symptoms mediated the relationship between higher cannabis use and increases in APPS. Negative and aggression symptoms, context of cannabis use, and using cannabis to cope with unpleasant affect mediated the relationship between cannabis use and high-D-APPS status. Results indicate that individual and contextual-level characteristics may contribute to the relationship between cannabis use and psychosis.