Associations between drinking context and simultaneous marijuana use among underage drinkers

Purpose: Drinking context (e.g., the source of alcohol, where alcohol was consumed, the number of people an individual drank with) is associated with quantity of alcohol consumed and the level of risk, particularly among underage drinkers. However, it is unclear how contextual factors may be associated with simultaneous use of marijuana while drinking. Simultaneous alcohol and marijuana use is associated with more negative consequences experienced compared to consuming either substance alone. This study extends previous literature by examining associations between contextual factors of underage drinkers' most recent drinking episode and whether they simultaneously used marijuana, using a nationally representative sample. Methods: National Survey of Drug Use and Health data from 2010 - 2019 were used. The sample consisted of past-month drinkers under 21 years old (n = 40,128 unweighted; N = 7,707,382 weighted for nationally representative estimates). Multivariable logistic regression models were used. Results: Compared to those getting alcohol from their parents, those who were given it for free (OR = 2.659, 95% CI = 2.312, 3.059), paid someone else to buy it (OR = 3.268, 95% CI = 2.762, 3.861), purchased it themselves from a store (OR = 4.284, 95% CI = 3.435, 5.349), or got it some other way (OR = 2.115, 95% CI = 1.822, 2.689) had higher odds of engaging in simultaneous alcohol and marijuana use. The number of people the participant drank with was not statistically significantly associated with simultaneous alcohol and marijuana use. Compared to those drinking in their own home, those who drank in a bar (OR = 0.664, 95% CI=0.495, 0.890) or in an 'other' location (OR = 0.802, 95% CI=0.691, 0.931) had significantly lower odds of engaging in simultaneous alcohol and marijuana use, whereas those who drank in someone else's home (OR=1.373, 95% CI = 1.168, 1.614) or in more than one location (OR = 1.914, 95% CI = 1.458, 2.512) had significantly higher odds of simultaneously using marijuana. Conclusions: Given the associations between alcohol access and drinking locations with simultaneous alcohol and marijuana use, policy-level interventions should be considered. Specifically, enforcement of age verification laws in places where alcohol or marijuana is purchased or consumed should be strengthened. This may be accomplished by increasing the frequency of compliance checks for age verification at these retail locations. Furthermore, limiting the alcohol and marijuana outlet density, particularly in areas with a high population of underage drinkers (e.g., near colleges), may decrease the prevalence of underage use. Increasing prices and taxation of alcohol and cannabis products may also decrease prevalence of use, particularly among young adults with limited income. Lastly, increasing enforcement of social host liability and sales to minors laws to hold adults providing substances to young people legally accountable may decrease sale to underage individuals. These strengthened legal and enforcement efforts may increase barriers related to purchasing or using alcohol and marijuana among those under 21.