Sources of alcohol and associations with drinking frequency and binge drinking among a large sample of adolescents.

Background: Underage drinking remains a major public health concern worldwide, contributing to a wide range of health and social harms. While adolescent alcohol use has been widely studied, there is limited evidence on how adolescents obtain alcohol and how these sources relate to drinking behaviours. Methods: This cross-sectional analysis used data from 8,507 Grades 9-12 students participating in the 2022-2023 COMPASS study across 66 schools in Canada. Analyses were restricted to students who reported alcohol use in the past 12 months. Proportional odds mixed models assessed associations between alcohol sources and two ordinal outcomes: drinking frequency and binge drinking frequency, adjusting for individual- and school-level covariates. Results: Parents/guardians were the most frequently reported source of alcohol (32%), followed by parties or events (22%) and purchasing or receiving alcohol from others (17%). Parental provision was most common among occasional or infrequent drinkers, whereas commercial sources (stores, restaurants, or bars) were prominent among frequent drinkers and binge drinkers. Adjusted models showed that obtaining alcohol from commercial sources was associated with a more than a fivefold increase in the odds of frequent and binge drinking compared with parental supply. Conclusions: These findings highlight distinct patterns in how Canadian adolescents report accessing alcohol, underscoring the importance of prevention strategies that address both social and commercial sources. Interventions focused on family environments, party settings, and retail access may help reduce opportunities for alcohol acquisition and mitigate the risk of higher-risk drinking behaviours among youth.