Patterns of Simultaneous and Concurrent Alcohol and Marijuana Use Among Adolescents

Introduction. Alcohol and marijuana are the two most commonly used substances among adolescents. Recent research has highlighted the risks associated with simultaneous use (i.e., using alcohol and marijuana so that their effects overlap), including higher rates of traffic accidents. Although the majority of adults use alcohol and marijuana simultaneously rather than concurrently (i.e., separately; Subbaraman, & Kerr, 2015) and simultaneous use is reported by 23% of 12^th graders in the US (Terry-McElrath et al., 2013), very little is known about the patterns of concurrent and simultaneous alcohol and marijuana use among adolescents.

Methods. Latent class analysis (LCA) was used to examine the patterns of alcohol use (none in the past year, use in the past year but no binge drinking in the past two weeks, binge drinking), marijuana use (none in the past year, use in the past year but not past 30 days, past 30-day use), and simultaneous use such that the effects overlap (in the past year). Data were drawn from nationally representative cross-sectional samples of 12th grade students from 1976-2016 in the Monitoring the Future study. Respondents included in the analysis (N=84,805; 48.7% male, 74.8% White) were a random one-sixth of the sample who were asked about simultaneous alcohol and marijuana use during the past year. Respondents who never used alcohol or marijuana in the past year (21%) were excluded from the LCA.

Results. A four-class solution provided the best fit to the data. Classes were: (1) Alcohol-only use (60%); (2) Simultaneous alcohol and marijuana use with binge drinking and recent marijuana use (SAM-heavy use; 11%); (3) Simultaneous alcohol and marijuana use with recent marijuana use (SAM-lighter use; 22%); and (4) Marijuana use with past year alcohol use (7%). Individuals in the SAM use classes were more likely to be male and White, compared to those in other classes. Furthermore, those in the SAM-heavy use class were more likely to be male, White and have parents with lower education, compared to those in the SAM-lighter use class.

Conclusions. Findings from this study show heterogeneity in patterns of simultaneous and concurrent alcohol and marijuana use. Among 12^th graders who use both alcohol and marijuana, the majority use simultaneously.