Cannabis Potency Effects on Brain White Matter in Early Phase Psychosis

Canada reports some of the highest rates of cannabis use in our youth and young adult populations, among all the developed countries. Recent Health Canada surveys report that 27% of 16-19-year-olds and 32% of 20-24-year-olds have used cannabis in the past 30 days, with 16-24-year-olds showing the highest rates of daily or near-daily use. Unfortunately, cannabis use has also been found to be a risk factor for the development of a psychotic disorder in emerging adults, and in those who develop psychosis and continue cannabis use, there is a significant effect on long term outcomes. This includes the severity of symptoms, risks of relapse (being hospitalized) and not reaching a level of functioning that would be expected. Lifetime experience with cannabis is greater than 80% in young adults with early phase psychosis (EPP; the first 5 years of a psychosis illness) with up to 30% of Canadian EPP patients meeting criteria for a diagnosis of cannabis use disorder (CUD) at entry to care. A recent Canadian population-based study found that cannabis use disorder associated to psychosis has risen from 3.7% pre-2018 to 10.3% at present. There has been a significant increase in Δ9-tetrahydrocannabinol (THC) levels in cannabis products available globally over the years, with popular cannabis products available start as high as 18% THC in Canada. However high potency cannabis carries a more significant risk for psychosis development, as well as higher risk for cannabis dependence and other severe mental health issues. A major gap in the research is a specific focus on cannabis potency on brain white matter (WM) in youth and young adults, and if there are any potential treatment strategies that could be used to influence any of these cannabis WM effects. To address this, a medication called metformin, that is already used in psychosis to help with side effects of antipsychotic medications, will be used as it has also shown promise to influence WM changes in other illnesses. This project is thus focused on naturalistic cannabis potency effects on WM in emerging adults in EPP (divided into three groups; those using high potency cannabis, low potency cannabis, and minimal cannabis use) and treating them with metformin for 6 months and assessing effects on neuroimaging, cognitive and clinical variables. The purpose of this pilot feasibility study is to inform the development/refinement of an intervention protocol, and not to test potential effects or mechanisms as the sample size will have insufficient power to perform an in-depth analysis. The results of this work will inform our research strategy development and assess feasibility of our novel methodological approach. Participants will: 1. Visit the clinic at baseline, 3 months (only Timeline Follow-Back Assessment administered), and 6 months post baseline to complete substance use and mental health questionnaires, and cognitive assessments 2. Complete an MRI scan at baseline and 6 months 3. Take Metformin every day for 6 months