“Dynamics of friendship networks and alcohol use in early and mid adolescence.”
By Liesbeth Mercken, Christian Steglich, Ronald Knibbe, and Hein de Vries, 2011.
Journal of Studies on Alcohol and Drugs 73, 99-110.

Objective: Similarity in alcohol consumption among adolescent friends could be caused by influence of friends or by selection of similar alcohol consuming friends. This paper aims to disentangle influence and selection processes, while specifically examining changes over time in these processes and possible differences between reciprocal and non-reciprocal friendships. Method: The design was longitudinal with 4 observations (T1-T4). Data consisted of a longitudinal sample of 1204 Finnish adolescents in 10 junior high schools. The main measurements were adolescents' friendship networks and alcohol consumption. For three successive time periods (mean age T1= 13.6, T2= 14.6, T3= 15.6, T4=16.1), actor-based models for the co-evolution of networks and behavior were analyzed. Results: Selection as well as influence processes played an important role in adolescent alcohol consumption. Influence was found during the first period whereas support for selection was found during the last two time periods. The strength of influence and selection processes did not differ for reciprocal and nonreciprocal friendships. Conclusions: The impact of selection and influence processes changed over time in such that influence was only present during early adolescence whereas selection during mid adolescence. During early adolescence youngsters would benefit from learning to resist social influence. Alcohol consumption prevention programs targeting mid adolescence should consider peer selection processes. These findings stress the importance of considering changes over time in future practice and research.

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