LAUSR

Importance Recent information on the trends in past-year alcohol abstinence and marijuana abstinence, co-use of alcohol and marijuana, alcohol use disorder, and marijuana use disorder among US young adults is limited. Objectives To assess national changes over time in past-year alcohol and marijuana abstinence, co-use, alcohol use disorder, and marijuana use disorder among US young adults as a function of college status (2002-2018) and identify the covariates associated with abstinence, co-use, and marijuana use disorder in more recent cohorts (2015-2018). Design, Setting, and Participants This study examined cross-sectional survey data collected in US households annually between 2002 and 2018 as part of the National Survey on Drug Use and Health. The survey used an independent, multistage area probability sample for all states to produce nationally representative estimates. The sample included 182 722 US young adults aged 18 to 22 years. The weighted screening and weighted full interview response rates were consistently above 80% and 70%, respectively. Main Outcomes and Measures Measures included past-year abstinence, alcohol use, marijuana use, co-use, alcohol use disorder, marijuana use disorder, prescription drug use, prescription drug misuse, prescription drug use disorder, and other drug use disorders based on Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria. Results The weighted sample comprised 51.1% males. Between 2002 and 2018, there was an annual increase in past-year alcohol abstinence among young adults (college students: 0.54%; 95% CI, 0.44%-0.64%; non-college students: 0.33%; 95% CI, 0.24%-0.43%). There was an annual increase in marijuana use from 2002 to 2018 (college: 0.46%; 95% CI, 0.37%-0.55%; non-college: 0.49%; 95% CI, 0.40%-0.59%) without an increase in marijuana use disorder for all young adults. Past-year alcohol use disorder decreased annually (college: 0.66%; 95% CI, 0.60%-0.74%; non-college: 0.61%; 95% CI, 0.55%-0.69%), while co-use of alcohol and marijuana increased annually between 2002 and 2018 among all young adults (college: 0.60%; 95% CI, 0.51%-0.68%; non-college: 0.56%; 95% CI, 0.48%-0.63%). Young adults who reported co-use of alcohol and marijuana or met criteria for alcohol use disorder and/or marijuana use disorder accounted for 82.9% of young adults with prescription drug use disorder and 85.1% of those with illicit drug use disorder. More than three-fourths of those with both alcohol use disorder and marijuana use disorder reported past-year prescription drug use (78.2%) and illicit drug use (77.7%); 62.2% reported prescription drug misuse. Conclusions and Relevance The findings of this study suggest that US colleges and communities should create and maintain supportive resources for young adults as the substance use landscape changes, specifically as alcohol abstinence, marijuana use, and co-use increase. Interventions for polysubstance use, alcohol use disorder, and marijuana use disorder may provide valuable opportunities for clinicians to screen for prescription drug misuse.