Chain reactions in adolescents' cigarette, alcohol and drug use: similarity through peer influence or the patterning of ties in peer networks?

Similarity in substance use among adolescents and their peers is usually attributed to peer influence or, occasionally, to either peer influence or selection. This paper suggests that similarity is due to both peer influence and selection. For some adolescents, peer influence outside the chain occurs first and selection follows; for others, selection occurs first and peer influence within the chain follows. Whichever occurs first, all adolescents are selected and nearly all are influenced. Peer networks contribute to similarity by providing a pattern of peer ties in which peer influence can flourish. Chain reactions result from the pattern and peer influence. (C) 2004 Elsevier B.V. All rights reserved.