| This dissertation addresses a fundamental question in social network analysis and sociology: whether and to what extent peers affect a person's wellbeing. More specifically, it attempts to identify and quantify peer effects on smoking among adolescents.;Previous theoretical and empirical works on peer effects were reviewed and a systematic framework to study causal peer effects was developed to distinguish several types of peer effects. To overcome the various difficulties in studying peer effects with observational data, a novel field experiment was conducted with a partial treatment group design specifically tuned to estimate peer effects.;More specifically, a smoking prevention intervention composed of distributing smoking prevention brochures and hosting health education workshops was assigned to partial randomly chosen members in a certain number of classes in six middle schools in China where the experiment was fielded. The goal was to study how the information contained in the intervention was spread across students and how it affected their information, knowledge, intention, and behavior regarding smoking. To accelerate or reinforce the diffusion, central students or students with their close friends as identified based on their social network information were also chosen respectively to receive the intervention in different treated classes.;Descriptive analysis provided strong support for peer effects on the initiation and maintenance of adolescent smoking. Further regression analysis showed that compared with students in the control classes, students whose classmates were randomly chosen to receive the intervention but who did not receive the intervention themselves were more likely to exchange information about the intervention with other students and to remain non-smokers or change to non-smokers. It was also found that the social network-based interventions did not consistently bring significant added value in all the outcomes of interest and their benefits mainly concentrated on lowering students' intention to smoke and decreasing smokers' popularity.;Interviews with teachers and students revealed that a culture of sharing cigarettes and a misperception of viewing smoking as a personal ability or friendship enhancer were two of the main mechanisms by which peer influence on adolescent smoking unfolded.;Limitations of this research and future research directions were also discussed. |
