Project 465637

One in three Canadian youth (15-24 years) used cannabis in 2020. Early or heavy cannabis use (CU) has been linked to poorer brain functioning, which can persist beyond acute cannabis intoxication. In turn, this poorer brain functioning has been linked to worse outcomes including poorer academic performance and work capacity. However, previous studies are limited, with very few of these following participants repeatedly across development and taking important factors into account (e.g., different modes/profiles of CU, polysubstance use, key school and demographic factors). Thus, we still do not know whether youth with certain cognitive profiles are at increased risk of CU or whether youth CU leads to poorer brain function. Clarifying this developmental sequence will allow for the identification of youth most at risk of CU and neurocognitive problems, which will in turn help to better inform policy, treatment, and prevention programs. This study will benefit from 25+ years of data collected from two birth cohorts of the Québec Longitudinal Study of Child Development (N=240 born in 1996/7 and N=1500 born 1997/8), to examine associations between CU and brain function across youth, a key population identified as a priority research area by the Canadian Institutes of Health Research. Namely, this proposal will examine the bidirectional relationship between CU (alone and in the context of other substance use) and neurocognitive function, and whether this association differs according to sex, gender and sexual orientation. Importantly, this study will also account for influential factors associated with CU and neurocognition, including brain function prior to cannabis and other substance use onset, as well as educational, psychological (e.g., mental health) and family factors (e.g., history of substance use). Finally, the current study will also bridge gaps in knowledge translation by developing and disseminating engaging psychoeducational materials.