Peer influence decay and behavioral diffusion in adolescent networks: A simulation approach.

How far does peer influence spread through social networks before dissipating? This study investigates the diffusion of smoking behavior in adolescent friendship networks using longitudinal data from two schools (n = 3154 students) in the National Longitudinal Study of Adolescent to Adult Health. Using Stochastic Actor–Oriented Models, we simulate interventions targeting heavy smokers using various strategies (random, in-degree, eigenvector centrality) and coverage (10 to 100%). A new exponential decay model quantifies influence attenuation, revealing indirect peer influences, or spillover effects, up to three steps from targets. Targeting 10 to 30% of central individuals maximizes smoking reductions, but gains plateau beyond 40 to 50% owing to network saturation. In our analyses, the denser network exhibits broader diffusion and slower decay than the larger, sparser network. This decay metric optimizes intervention design across diverse network structures. Editor's summary: Cigarette smoking in teens spreads through friends of friends. This influence dissipates or decays along degrees of separation and is bidirectional, because people are simultaneously influenced by smokers and nonsmokers. But how quickly does peer influence decay, and does network shape matter? Wang et al. simulated smoking reduction interventions in two public secondary schools with very different parameters. Across schools, intervention effects were most impactful when small groups (10 to 30%) of well-connected, heavy smokers were targeted. However, context matters: Their influence spread more broadly and decayed more slowly in dense networks, suggesting that different policies are warranted in fragmented networks. —Ekeoma Uzogara [ABSTRACT FROM AUTHOR]