Selecting, retaining, and socializing friends

Friends have been implicated in the acquisition of adolescent substance use, but little attention has been given to how the origins of substance use similarity vary across groups. The first aim of this study is to examine whether friend selection, de-selection, and socialization differ as a function of friendship group's substance use. The second aim of this study is to extend Simulation Investigation for Empirical Network Analyses (SIENA) by demonstrating how group-level interactions can be included in the mode, and to demonstrate a new method to follow-up statistically significant group-level interactions in SIENA. Participants include 1419 Finnish students (729 females, 690 males) from upper secondary schools in Finland. Two waves of data were collected, starting when most participants were between 15 and 17 years of age. Waves of data collection were separated by one year. Results indicate that friends are selected, deselected, and socialized for substance use. Follow-up illustrations indicate that the magnitude of these processes vary as a function of substance use in the friendship group.