Co-use of alcohol and e-cigarettes and the role of social influences during drinking events among young adults: A day-level study

BACKGROUND: Alcohol and e-cigarettes are commonly used among young adults (YAs), and many co-use both substances. Social influences strongly predict the individual use of alcohol and e-cigarettes, but their role in co-use remains unexplored. We hypothesized that drinking (vs. non-drinking) days are associated with increased risk of being offered and using e-cigarettes, and there is a positive association between total drinks consumed and e-cigarette use. We also hypothesized that passive (being with/around someone using e-cigarettes while drinking) and active (being offered e-cigarettes while drinking) social influences are associated with increased risk of e-cigarette use, and the relationship between total drinks consumed and e-cigarette use is stronger with exposure to such social influences. METHODS: YAs aged 19-30 who drink heavily (N = 154; 63.0% female; 84.4% White; all recruited from the Northeast U.S.) completed 28 days of daily assessments. Morning reports asked about prior-day alcohol use, e-cigarette use, and social influences. RESULTS: Participants reported 1371 drinking days (33.4% of all days), of which 199 (14.5%) were co-use days and 120 (8.8%) were characterized by e-cigarette offers. Drinking (vs. non-drinking) days were associated with greater risk of being offered and using e-cigarettes. On drinking days, total drinks consumed and social influences were positively associated with e-cigarette use. No interaction effects between total drinks consumed and social influences were found. CONCLUSIONS: Alcohol use and quantity are associated with same-day e-cigarette use, and social influences may contribute to YAs' e-cigarette use while drinking. Interventions should consider drinking events as high-risk environments for e-cigarette offers and use.