Grant: Team Grant: The Canadian Cannabis and Brain Health Consortium

In 2018, Canada became the first major developed nation to legalize non-medical cannabis. Since then, cannabis products with high levels of THC and low levels of CBD have become widely available. Recent federal reviews have identified major gaps in knowledge about the long-term effects of these products on mental health and cognitive functioning, particularly among vulnerable populations. People living with epilepsy are of special concern. This neurological condition affects approximately 300,000 Canadians, many of whom experience memory problems, anxiety, or depression. Despite this vulnerability, up to half of people with epilepsy report using non-medical cannabis, often without medical supervision, even though THC products do not treat seizures and may worsen cognitive or psychiatric symptoms. This project aims to improve understanding of how non-medical cannabis is used in Canada and how it affects mental health and cognitive functioning over time, both in the general population and among people with epilepsy. We will conduct two complementary longitudinal studies across three sites: (1) a population-based cohort representing adults from the general population, and (2) an enriched sub-cohort of people with epilepsy. Using harmonized methods will allow us to distinguish common patterns of use from those associated with increased mental health and cognitive risks. Participants in both cohorts will complete questionnaires on cannabis use, mental health, and daily functioning. Subgroups will also undergo in-person cognitive assessments to objectively measure brain health across adulthood. The findings will provide critical evidence to inform public health policy, clinical guidance, and harm-reduction strategies. By identifying higher-risk patterns of use, particularly exposure to high-THC products, this project will support safer cannabis use and better health outcomes for Canadians, especially those living with epilepsy.