Grant: TG:The CND Cannabis/Brain Health Cons-Interv Trials to reduce Cannabis use/Harms

Despite its high prevalence, the impacts of cannabis use on brain health remain poorly understood, due to most studies having small sample sizes and cross-sectional designs. The Canadian Cannabis and Brain Health Consortium (CCBHC) is a major national initiative to address this gap. Specifically, the CCHBC will be composed of ten projects, each comprising a cohort study and a research study, with the aggregation of all ten creating a developmentally-informed longitudinal cohort of 3000+ population-representative individuals. This project will address the CCHBC priorities for both the cohort study and the research study. First, for the cohort study, we will leverage two ongoing longitudinal cohort studies, both led by led by NPA MacKillop, to examine relations between cannabis use and multi-modal brain health measures over a 12-month period. This longitudinal design examining changes in cannabis use and brain outcomes will address a significant limitation of most existing studies. Second, for the research study, one CCHBC priority domain is intervention research and, based on our favourable pilot study, we will conduct a randomized controlled trial (RCT) on psilocybin treatment for cannabis use disorder (CUD). As there is a high need for effective treatments for CUD and are no medications approved currently, this addresses a significant gap. Importantly, the CCHBC sub-components are expected to be harmonized together, which this project will achieve by combining 300 population-representative adults with the CUD+ participants in the RCT to make up the cohort sample. Thus, the aggregated cohort sample will both be largely representative but also enriched with individuals with CUD, the group most likely to experience adverse brain effects from cannabis. Collectively, these two components will make major contributions to the CCBHC and, more broadly, to both understanding cannabis impacts on the brain and the viability of a novel promising treatment for CUD.