title: The interplay of friendship networks and social networking sites: longitudinal analysis of selection and influence effects on adolescent smoking and alcohol use.
abstract: OBJECTIVE
  We examined the coevolution of adolescent friendships and peer influences with respect to their risk behaviors and social networking site use.
  
  
  METHODS
  Investigators of the Social Network Study collected longitudinal data during fall 2010 and spring 2011 from 10th-grade students in 5 Southern California high schools (n = 1434). We used meta-analyses of stochastic actor-based models to estimate changes in friendship ties and risk behaviors and the effects of Facebook and MySpace use.
  
  
  RESULTS
  Significant shifts in adolescent smoking and drinking occurred despite little change in overall prevalence rates. Students with higher levels of alcohol use were more likely to send and receive friendship nominations and become friends with other drinkers. They were also more likely to increase alcohol use if their friends drank more. Adolescents selected friends with similar Facebook and MySpace use habits. Exposure to friends' risky online pictures increased smoking behaviors but had no significant effects on alcohol use.
  
  
  CONCLUSIONS
  Our findings support a greater focus on friendship selection mechanisms in school-based alcohol use interventions. Social media platforms may help identify at-risk adolescent groups and foster positive norms about risk behaviors.
authors.affiliation: Grace C. Huang, Daniel Soto, and Thomas W. Valente are with the Institute for Prevention Research, Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles. Kayo Fujimoto is with the Division of Health Promotion and Behavioral Sciences, School of Public Health, University of Texas at Houston.
authors.forename: Grace C
authors.initials: GC
authors.lastname: Huang
authors.forename: Daniel
authors.initials: D
authors.lastname: Soto
authors.forename: Kayo
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Valente
mesh_terms: D000293:Adolescent; D000428:Alcohol Drinking / Q000453:epidemiology* / Q000523:psychology; D002140:California / Q000453:epidemiology; D005260:Female; D033062:Friends / Q000523:psychology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010379:Peer Group; D015995:Prevalence; D012309:Risk-Taking; D012907:Smoking / Q000453:epidemiology* / Q000523:psychology; D061108:Social Media / Q000706:statistics & numerical data*; D060756:Social Networking