Higher education among the “forgotten half”:  The association between substance use and college completion among 2-year college students versus matched 4-year college students from a nationally representative longitudinal study

Abstract

Background: Recent policy changes have increased marijuana availability to college students. Past research has not evaluated the association between substance use and college completion among the forgotten half of disadvantaged young adults who access higher education through 2-year colleges. Methods: This study uses a subsample of college-enrolled participants from the National Longitudinal Study of Adolescent and Adult Health to evaluate whether substance use in 2001 among students attending 2-year college and 4-year college predicts educational attainment in 2008. We used Mahalanobis nearest-neighbor and exact matching within propensity score calipers to identify a comparison group of 4-year college students (n=888) similar to the 2-year college students (n=1398) on 15 baseline measures including grades, test scores, and substance use. We used multivariate regression in the matched sample using a Poisson working model to estimate the relative risk of earning no post-secondary degree.Results: Compared with matched 4-year college students, 2-year college students were more likely to use methamphetamines, cocaine, marijuana, and more likely to report problematic substance use, and less likely to use alcohol. Two-year college students who used methamphetamines in the past year (IRR=1.51, 95% CI (1.12, 2.04), p=0.007) or past month (IRR=1.69, 95% CI (1.09, 2.61), p=0.02), or completed alcohol abuse treatment (IRR=1.58, 95% CI (1.21, 2.07), p<0.001) were less likely to complete college. Four-year college students who reported that drugs interfered with school or work in the past year (IRR=1.84 (1.28, 2.64), p=0.001), used cocaine in the past year (IRR=1.47 (1.04, 2.08), p=0.03), and used marijuana in the past year (IRR=1.30 (1.07, 1.57), p=0.007), past month (IRR=1.31 (1.07, 1.61), p=0.01), or ≥5 times in the past month (IRR=1.44 (1.12, 1.85) p=0.005) were less likely to complete college. Conclusions: Substance use interventions should target 2-year and 4-year college students. Two-year colleges that better accommodate students who complete substance use treatment may improve these students’ completion. Students who use marijuana or cocaine or whose drug use impairs functioning may benefit from an incremental approach of completing a 2-year degree prior to transfer for a 4-year degree, rather than enrolling directly in a 4-year program.