title: Peer influences: the impact of online and offline friendship networks on adolescent smoking and alcohol use.
abstract: OBJECTIVE
  Online social networking sites (SNSs) have become a popular mode of communication among adolescents. However, little is known about the effects of social online activity on health behaviors. The authors examined the use of SNSs among friends and the degree to which SNS activities relate to face-to-face peer influences and adolescent risk behaviors.
  
  
  METHODS
  Longitudinal egocentric friendship network data along with adolescent social media use and risk behaviors were collected from 1,563 10th-grade students across five Southern California high schools. Measures of online and offline peer influences were computed and assessed using fixed-effects models.
  
  
  RESULTS
  The frequency of adolescent SNS use and the number of their closest friends on the same SNSs were not significantly associated with risk behaviors. However, exposure to friends' online pictures of partying or drinking was significantly associated with both smoking (β = .11, p < .001) and alcohol use (β = .06, p < .05). Whereas adolescents with drinking friends had higher risk levels for drinking, adolescents without drinking friends were more likely to be affected by higher exposure to risky online pictures (β = -.10, p < .05). Myspace and Facebook had demographically distinct user characteristics and differential effects on risk behaviors.
  
  
  CONCLUSIONS
  Exposure to risky online content had a direct impact on adolescents' risk behaviors and significantly interacted with risk behaviors of their friends. These results provide evidence that friends' online behaviors should be considered a viable source of peer influence and that increased efforts should focus on educating adolescents on the negative effects of risky online displays.
authors.affiliation: Institute for Health Promotion and Disease Prevention Research, Department of Preventive Medicine, School of Medicine, University of Southern California, Los Angeles, California. Electronic address: grace.huang@nih.gov.
authors.forename: Grace C
authors.initials: GC
authors.lastname: Huang
authors.affiliation: Institute for Health Promotion and Disease Prevention Research, Department of Preventive Medicine, School of Medicine, University of Southern California, Los Angeles, California.
authors.forename: Jennifer B
authors.initials: JB
authors.lastname: Unger
authors.affiliation: Institute for Health Promotion and Disease Prevention Research, Department of Preventive Medicine, School of Medicine, University of Southern California, Los Angeles, California.
authors.forename: Daniel
authors.initials: D
authors.lastname: Soto
authors.affiliation: Division of Health Promotion and Behavioral Sciences, School of Public Health, University of Texas at Houston, Houston, Texas.
authors.forename: Kayo
authors.initials: K
authors.lastname: Fujimoto
authors.affiliation: Institute for Health Promotion and Disease Prevention Research, Department of Preventive Medicine, School of Medicine, University of Southern California, Los Angeles, California.
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Pentz
authors.affiliation: School of Social Work, University of Southern California, Los Angeles, California.
authors.forename: Maryalice
authors.initials: M
authors.lastname: Jordan-Marsh
authors.affiliation: Institute for Health Promotion and Disease Prevention Research, Department of Preventive Medicine, School of Medicine, University of Southern California, Los Angeles, California.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Valente
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D000428:Alcohol Drinking / Q000453:epidemiology / Q000523:psychology*; D003142:Communication; D005260:Female; D033062:Friends / Q000523:psychology*; D006801:Humans; D020407:Internet; D008137:Longitudinal Studies; D008297:Male; D010379:Peer Group; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology / Q000523:psychology*; D012932:Social Facilitation; D012944:Social Support
keywords: Adolescent; Adolescent drinking; Alcohol drinking; Friends; Peer influence; Smoking; Social media; Social network analysis