Simultaneous alcohol and marijuana use among underage young adults in the United States

Objective: The current study examines the prevalence, stability, and correlates of simultaneous alcohol and marijuana (SAM) use among underage US young adults, a population at high risk for participating in this behavior. Method: Analyses used data from 1719 respondents (46.8% men) who participated in the nationally representative 12th-grade Monitoring the Future study and provided responses to SAM use items at longitudinal follow-up at modal ages 19/20 between 2007 and 2016. Prevalence estimates and covariate associations with SAM use were estimated. Results: SAM use prevalence at modal age 19/20 was 22.5%. Multivariable models indicated that odds of age 19/20 SAM use were significantly (p < .05) higher for men (vs. women) and for respondents who started alcohol use by age 18 (vs. those who delayed uptake until after high school). Odds of SAM use were especially high for individuals attending college full-time and not living with parents. Among those who reported SAM use at modal age 18, 56.2% continued to report SAM use at modal age 19/20. Among those who did not report SAM use at modal age 18, only 14.2% reported SAM use at modal age 19/20. Conclusions: SAM use among young adults aged 19/20 in the US is relatively common, but especially so for those who began such use by age 18, highlighting the early onset and stability of this behavior. Among underage drinkers, SAM risk varies by sex, race/ethnicity, college status, and living arrangements.