Cannabis use and attenuated positive and negative symptoms in youth at clinical high risk for psychosis.

Cannabis use is more prevalent among youth at clinical high-risk (CHR) for psychosis than healthy controls (HC). There is mixed evidence as to whether cannabis use is associated with increased severity of attenuated psychotic symptoms (APS) or whether current cannabis use is associated with the transition to psychosis. This study aims to assess cannabis use differences between CHR youth and HC and the impact of cannabis use on APS, clinical status, and transition to psychosis. Participants were from the North American Prodrome Longitudinal Study-3, a prospective longitudinal study including 710 individuals, age 12-30, meeting criteria for a psychosis risk syndrome based on the Structured Interview for Psychosis-Risk Syndromes, and 96 HC. Cannabis use, frequency, and severity of use were assessed with the Alcohol Use Scale/Drug Use Scale. Current and past cannabis use disorders were assessed with the Structured Clinical Interview for DSM-5. Compared to HC, CHR individuals reported significantly increased lifetime cannabis use, during the past six months, and at baseline; greater frequency and severity of cannabis use; and increased prevalence of cannabis use disorder. Relative to CHR youth without cannabis use, CHR cannabis users had significantly higher ratings on baseline grandiosity and lower 12-months social anhedonia. Severity of cannabis was unrelated to clinical status at 2-years, and it did not differentiate CHR individuals who transitioned to psychosis from those who did not. However, a major limitation was that the current number of CHR cannabis users was small, and survival analyses resulted in a smaller power than the 80 % recommended.