Abstract
OBJECTIVE: We investigate how alcohol use and friendship co-evolve during students' transition to university. We discern effects of peer influence from friend selection based on alcohol use, whether such effects vary in strength across the school year, and whether alcohol has different effects on friendship formation versus friendship maintenance. METHOD: We gathered data on friendships, alcohol use, and binge drinking from 300 residence hall students (71% female) at a large, public U.S. university. Surveys were conducted at four time points during the 2015-2016 academic year. We used a stochastic actor-oriented model to test whether alcohol use was influenced by one's friends, while simultaneously testing for friend selection based on alcohol use and related network processes. RESULTS: Students were 7.0 times more likely to drink alcohol weekly if all versus none of their friends drank weekly and 6.8 times more likely to binge drink when all versus none of their friends engaged in binge drinking, after we controlled for friend selection. Alcohol use differentially affected friendship creation and maintenance in a complex manner: (a) weekly drinkers were more likely to form new friendships and dissolve existing friendships than nondrinkers and (b) similarity on drinking fostered new friendships but had no effect on friendship persistence. CONCLUSIONS: Friends influence one another's weekly drinking and binge drinking, whereas conversely, alcohol use contributes to both friendship formation and friendship instability.