The academic consequences of marijuana use during college

Abstract

Although several studies have shown that marijuana use can adversely affect academic achievement among adolescents, less research has focused on its impact on postsecondary educational outcomes. This study utilized data from a large longitudinal cohort study of college students to test the direct and indirect effects of marijuana use on college grade point average (GPA) and time to graduation, with skipping class as a mediator of these outcomes. A structural equation model was evaluated taking into account a variety of baseline risk and protective factors (i.e., demographics, college engagement, psychological functioning, alcohol and other drug use) thought to contribute to college academic outcomes. The results showed a significant path from baseline marijuana use frequency to skipping more classes at baseline to lower first-semester GPA to longer time to graduation. Baseline measures of other drug use and alcohol quantity exhibited similar indirect effects on GPA and graduation time. Over time, the rate of change in marijuana use was negatively associated with rate of change in GPA, but did not account for any additional variance in graduation time. Percentage of classes skipped was negatively associated with GPA at baseline and over time. Thus, even accounting for demographics and other factors, marijuana use adversely affected college academic outcomes, both directly and indirectly through poorer class attendance. Results extend prior research by showing that marijuana use during college can be a barrier to academic achievement. Prevention and early intervention might be important components of a comprehensive strategy for promoting postsecondary academic achievement.

Figure 1. Schematic Depiction of Hypothesized Model of the Longitudinal Relationship between Marijuana Use, Skipping Class, GPA, and Time to College Graduation

Note. In addition to the mediation paths depicted here, we also tested all possible direct paths from the covariates to the intercept and slope variables (i.e., marijuana, skipping, GPA), and all possible direct paths from the intercept and slope variables to the distal outcome of time to graduation. The observed variables for the latent variables of intercept and slope for marijuana use frequency, skipping class, and GPA have been omitted from this figure for ease of presentation; refer to Figure 3A in the supplemental online materials for a more complete depiction of the trajectory component of the model and its parameterization.

Figure 2. Structure Coefficients (Standard Errors) for the Latent Variable Model of the Relationship between Intercept and Slope for Marijuana Use, Skipping Class, GPA, and Time to College Graduation

Note. All paths shown are statistically significant (p<.05). Non-significant paths were dropped from the model. For ease of presentation, additional significant paths between the covariates and the intercepts, slopes, and outcome were omitted from this figure, although they were retained in the model (see Table 3A in supplemental online materials for estimates of the structure coefficients and their standard errors, for significant paths that are not shown here). Baseline covariates that were included in the model were alcohol quantity and frequency, number of other drugs used during the past year, sex, race/ethnicity, parents’ education, living-learning program involvement, fraternity/sorority involvement, number of other extracurricular activities, impulsive sensation-seeking, behavioral dysregulation, depressive symptoms, and anxiety symptoms.