Simultaneous alcohol and marijuana (SAM) use, often defined as use of alcohol and marijuana together so that their effects overlap, is associated with acute injury (Duckworth and Lee, 2019, Gonçalves et al., 2022, Jackson et al., 2020, Terry-McElrath et al., 2014) and adverse interpersonal consequences (Lee et al., 2020, Linden-Carmichael et al., 2020, Subbaraman and Kerr, 2015), as well as long-term increased risk of substance use disorders (Conway et al., 2020, Lee et al., 2022, Terry-McElrath et al., 2013). In a typical year, approximately one fifth to one fourth of 12th grade students report past-year SAM, and 6–7% report frequent SAM (Lee et al., 2022). However, SAM prevalence began to decline in recent years among adolescents (Keyes et al., 2022a) while remaining stable or increasing among young adults (Terry-McElrath and Patrick, 2018).

The role of time trends in cigarette and nicotine use have potential implications for interpreting trends in SAM use. Lifetime cigarette use by the 12th grade peaked in the late 1970s, with 75.7% of high school seniors reporting at least some lifetime cigarette use at that time (Johnston et al., 2019). Over the next 40 years, cigarette use markedly declined, and as of 2020, only 24.0% of high school seniors have ever smoked cigarettes (Johnston et al., 2019). These time trends have implications for time trends in other substance use, because adolescents who use cigarettes and nicotine are a high risk group for subsequent alcohol and marijuana use (Keyes et al., 2016, Keyes et al., 2019, Roche et al., 2019). As cigarette prevalence has declined, more adolescents are in a lower risk group (those who do not use cigarettes) compared to a higher risk group (those who use cigarettes), thus lowering the risk of subsequent in alcohol and marijuana use through cigarette use (Miech et al., 2020, Miech et al., 2017).

Over the same time period, when examining the whole US adolescent population, alcohol use prevalence has substantially declined, and marijuana use has remained relatively stable (Johnston et al., 2019). Part of the mechanism underlying alcohol and marijuana use trends is the decline in cigarette use (Fleming et al., 2022, Fleming et al., 2016, Miech et al., 2017). Specifically, a greater proportion of adolescents are at lower risk for alcohol and marijuana use because cigarette smoking has declined. Thus, this suggests that cigarette use may be suppressing what would have been less of a decline for alcohol use, and even potential increases in prevalence for marijuana. Indeed, among adolescents who have used cigarettes, marijuana use prevalence is increasing; and among adolescents who have never used cigarettes, marijuana use prevalence is also increasing (Miech et al., 2017). These observed increases are suppressed when examining the overall US adolescent population because of the shift in composition of adolescents from high risk (ever used cigarettes) to low risk (never used cigarettes) (Miech et al., 2017).

Several issues remain unresolved with respect to SAM and overall patterns of alcohol and marijuana use, however, due to changing trends in other substances. The public health successes of reduced cigarette use have been partially offset by increases in nicotine use and nicotine use disorder among adolescents through vaping devices (Miech et al., 2021, Miech et al., 2019) since approximately 2015. Vaped nicotine use, like cigarette use, is associated with increased risk and frequency of subsequent alcohol and marijuana use (Evans-Polce et al., 2020, Park et al., 2020, Silveira et al., 2018). Thus, adolescents who vape nicotine may now again be shifting to a higher risk group for alcohol and marijuana use, and, potentially, SAM. Second, the extent to which cigarette and nicotine use may influence trends in SAM, as well as alcohol and marijuana use that is not used simultaneously, are complicated by other dynamics. Alcohol use has been declining among adolescents for decades (Jager et al., 2022, Platt et al., 2021), and recent declines in SAM use parallel declines in alcohol use (Lee et al., 2022). Thus, variation in trends examining SAM use, alcohol use without simultaneous marijuana use, and marijuana use without simultaneous alcohol use may exhibit heterogeneous trends by cigarette and vaped nicotine use. Overall, changes in more recent years when nicotine use has increased due to vaping (Miech et al., 2021), remain understudied.

In summary, SAM use remains prevalent and concerning for adolescent public health, especially in the context of underlying divergent trends in overall alcohol and marijuana use. The extent to which cigarette and nicotine use trends modify trends in SAM, as they do for marijuana and other substance use, has not been evaluated. Further, the extent to which trends in SAM use differ from trends in non-simultaneous alcohol and cannabis use remains understudied. The present paper: a) examines time trends in SAM use, and non-simultaneous use, from 2000 to 2020 among US 12th grade students controlling for demographics; and b) tests whether trends are modified by lifetime cigarette use or nicotine vaping, both together and separately. We examine SAM in the context of other patterns of alcohol and marijuana use given their disparate trends, providing a full account of alcohol-only (adolescents who have used alcohol but never marijuana); marijuana-only (adolescents who have used marijuana but never alcohol); non-simultaneous use (adolescents who have used both alcohol and marijuana, but never simultaneously); and no use (adolescents who have never used alcohol or marijuana).