Physical Health Disparities Associated with Trajectories of Marijuana Use Among Canadian Youth

Introduction: Research suggests youth consider marijuana a safe alternative to medication and youth cite health reasons as motives for use (McKiernan & Fleming, 2017). Yet, we have limited understanding of how early and frequent use of marijuana relates to health indicators in adolescence and young adulthood. Focusing on mainly young adults and cross sectional data, past research suggests associations between frequent marijuana use, poor subjective health, and reduced engagement in health-promoting behaviors (Ellickson, 2004; Smith et al., 2016). Associations are not significant between marijuana use and cardiometabolic risks (i.e., body mass index [BMI], waist circumference, blood pressure; Arria et al., 2016; Bechtold et al., 2015). Studies examining marijuana use and injuries are inconsistent; however, frequent marijuana use is associated with sexual risk behaviors (Patrick et al., 2012). In this study, we examine how developmental trajectories of marijuana use in Canadian youth, followed from ages 15 to 28, are related to a physical health indicators in both adolescence and young adulthood.

Method: Data were collected from a community-based sample of youth initially recruited in 2003 (N = 662; 48% male; ages 12 to18) and followed for six waves. Five trajectories of marijuana use (Abstainers-29%, Occasional users-27%, Decreasers-14%, Increasers-20%, and Chronic users-11%) were identified using latent class growth analysis. Health indicators included self-reported health indicators (physical symptoms and physical self-concept), health-promoting behaviors (physical activity, healthy eating practices, sleep duration), cardiometabolic risks (BMI, waist circumference, blood pressure), the number of serious injuries, and sexual risk behaviors (early sexual debut, number of sexual partners, and ever having a sexually transmitted disease [STI]). Multinomial logistic regression models using a three-step approach were used to compare health indicators among the trajectory groups in adolescence and young adulthood.

Results: Chronic users reported more physical symptoms, poorer physical self-concept, less physical activity, poorer eating practices, less sleep, earlier sexual debut, and higher number of sexual partners during adolescence than other groups. Chronic users continued to report more physical symptoms and less physical activity in young adulthood than all other groups, beyond adolescent levels. Chronic users also reported more acute health problems (i.e., serious injuries, early sexual debut, higher number of sexual partners, greater likelihood of having an STI) in young adulthood than all other groups.

Conclusions: Youth who engage in early, frequent, and continued use of marijuana use from adolescence to young adulthood are at-risk of physical health problems in adolescence and young adulthood. Education should dispel adolescents’ perceptions of marijuana as a safe and non-addictive way of treating pain. Adolescents’ complaints of physical symptoms and inquiry into their self-treatment could provide opportunities for assessing their marijuana use. Chronic users also report a higher number of acute health problems, injuries and STIs in young adulthood, contributing to costs of health care.