Behavioral Health, Mental Health, Substance Abuse
Age of Initiation of Marijuana Use and Academic Engagement during College
(UMD SPH Behavioral and Community Health Faculty )
Purpose: To extend prior research on marijuana’s association with academic performance deficits, and evidence that younger initiation of marijuana use predicts adverse health, economic, and interpersonal outcomes, the present study tests the hypothesis that early initiation would predict poorer class attendance during college and, thereby, lower grades. Methods: Data were collected in annual interviews with 1,253 undergraduate students who were originally recruited during their first year of college (87% response rate; 88-91% annual follow-up rates). Cumulative grade point average (GPA) in high school and college were obtained from university records, per informed consent. Responses from the first four years of college were averaged for past-year frequency of marijuana use and percentage of classes skipped. Hypothesized covariates were gender, race/ethnicity, and quantity and frequency of alcohol consumption at college entry. Findings: Age of initiation was categorized as early (ages 8 to 14, 12%), pre-college (ages 15 to 17, 46%), college (ages 18 to 22, 18%), and never (19%), with the remaining 5% excluded from analyses due to incomplete follow-up. Even accounting for demographics and alcohol, early initiators earned significantly lower GPAs in high school and skipped significantly more of their college classes relative to non-users (both ps<.01), and they used marijuana significantly more often than either pre-college or college initiators (p<.001). By college graduation, early initiators still had significantly lower GPAs than non-users (3.22 versus 3.36, p<.05), although this difference was attenuated after accounting for covariates. Structural model results supported a significant indirect path from early initiation to marijuana use frequency to skipping to college GPA (b=-.011, se=.003, p<.001), even accounting for high school GPA and other covariates. Discussion: Findings are consistent with other research on adverse outcomes among early-onset marijuana users. Skipping class was an important mediator of the association between early marijuana initiation and lower college GPA.