Simultaneous Alcohol and Marijuana Use Among College Students: Patterns, Correlates, and Norms

Background: Alcohol and marijuana users often engage in simultaneous alcohol and marijuana (SAM) use, which can result in more negative consequences than using either substance alone. Nevertheless, little is known about SAM use among contemporary college students to aid in the development of preventive interventions. In fact, no studies have yet investigated norms regarding SAM use. Because norms are often the targets of substance use interventions, obtaining accurate SAM use norms from college students and understanding how they relate to use patterns will be informative for the development of interventions targeting simultaneous use. We examined SAM use patterns, demographic correlates of SAM use, and normative influences on SAM use and related negative consequences among college students. Methods: In 2017 students who had used alcohol and marijuana in the past year were recruited from a random list of students attending three universities in states with different laws regarding recreational marijuana use (N = 1389). They completed an online survey, which assessed their own alcohol, marijuana, and SAM use and related consequences, their perceptions of the proportion of same-gendered peers and close friend who engaged in SAM use, and their demographic characteristics. Results: About three fourths reported at least one occasion of SAM use in the past year with an average frequency of twice per month among SAM users. There were significant differences in SAM use prevalence and frequency by sociodemographic characteristics controlling for past-year alcohol and marijuana frequency. Students in a state with decriminalized recreational marijuana use reported higher rates of past-year SAM frequency and higher perceived norms than students in states with legalized or criminalized use. There were also significant demographic differences in perceived norms regarding use among close friends and use among same-gender peers. Consistent with previous literature on alcohol and marijuana norms, students who engaged in SAM use endorsed significantly higher perceived peer and friend norms than those who did not. Also, higher perceived norms predicted more frequent SAM use and more negative consequences of use. Perceived SAM use by close friends was more strongly related to SAM use and consequences than perceived use by same-gender peer norms. Conclusions: Overall, the results indicate a need for prevention programs on college campuses that address SAM use. Personalized normative feedback interventions, which have been efficacious in reducing heavy drinking among college students, may also be effective be for SAM use.