196. THE EFFECTS OF EXTENDED CANNABIS ABSTINENCE IN YOUNG ADULTS WITH CO-OCCURRING CANNABIS USE DISORDER AND MAJOR DEPRESSION

Abstract Background Recreational cannabis use was legalized nation-wide in Canada in 2018, for people 19 years and older. There are considerable concerns about the effects of cannabis use on brain development and behavioral and mental health outcomes, including on the risk for, onset and course of psychiatric disorders, notable major depression. Aims & Objectives Our goal is to determine the effects of 28 days of biochemically-verified cannabis abstinence on clinical and cognitive outcomes in people with major depression. Method We are conducting a 4-year CIHR-funded controlled study of extended (28 day) cannabis abstinence on clinical and cognitive outcomes in N=100 participants with co-occurring cannabis use disorder and major depression, ages 18-55. A contingent reinforcement procedure (Lucatch et al., 2020) developed In our laboratory is used to facilitate cannabis abstinence. Cannabis abstinence was based on self-report, and biochemically-verified cannabis abstinenc Results To date, in the nascent sample (n=36; recruited primarily by social media and subway ads in downtown Toronto), the majority (29/36; ~80%) have been participants 19-35 years old, corresponding to late adolescent and emerging adulthood. Preliminary findings suggest that 28 days of produces clinically significant improvements (all p’s <0.03; Cohen’s d effect sizes >0.76) in depression, anxiety, anhedonia and selective aspects of neurocognition (e.g. working memory and sustained attention). Discussion & Conclusions Extended cannabis abstinence improves mood and cognitive outcome in young adults with major depression. These preliminary data have important biological, clinical and policy implications for understanding the links between cannabis addiction and depression in adolescents and emerging adults, and the development of treatments for this increasingly common co-morbidity.