title: Gender differences in friends' influences on adolescent drinking: a genetic epidemiological study.
abstract: BACKGROUND
  We use data from a population-based twin study to examine the association between characteristics of the friendship group and adolescents' own alcohol use at age 14, with focus on gender differences, both with respect to the adolescent's own gender and the gender composition of his/her friendship group.
  
  
  METHODS
  (1) We conducted analyses on the full epidemiological sample of individuals to determine the magnitude of association between friendship characteristics and alcohol use, and to test for interaction with gender and gender of friends. (2) We used the twin structure of the dataset to study the extent to which similarity in drinking behaviors between adolescents and their friends was due to shared genetic and/or environmental pathways.
  
  
  RESULTS
  Friends' drinking, smoking, and delinquency were more strongly related to alcohol use in girls, compared to boys, and in adolescents with opposite-sex friends, compared to adolescents with only same-sex friends. Friends' alcohol use showed modest evidence of genetic influence in girls, suggesting peer selection; however, there was no evidence of genetic influence on friends' alcohol use in boys. The correlation between adolescent and friend drinking was largely attributable to shared environmental effects across genders.
  
  
  CONCLUSIONS
  Gender and gender of friends moderate the associations between friends' behavior and adolescents' alcohol use, with evidence that girls, and those with opposite-sex friends, may be more susceptible to friends' influence. Genetically informative analyses suggest that similarity in alcohol use between adolescents and their friends is mediated, at least partially, through environmental pathways.
authors.affiliation: Washington University, St. Louis, Missouri, USA. ddick@vcu.edu
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Dick
authors.forename: Jason L
authors.initials: JL
authors.lastname: Pagan
authors.forename: Candice
authors.initials: C
authors.lastname: Holliday
authors.forename: Richard
authors.initials: R
authors.lastname: Viken
authors.forename: Lea
authors.initials: L
authors.lastname: Pulkkinen
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Rose
mesh_terms: D000293:Adolescent; D000428:Alcohol Drinking / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology*; D000704:Analysis of Variance; D003430:Cross-Sectional Studies; D005260:Female; D005387:Finland; D033062:Friends / Q000523:psychology*; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D005838:Genotype; D006306:Health Surveys; D006801:Humans; D007857:Leadership; D008137:Longitudinal Studies; D008297:Male; D010379:Peer Group; D010641:Phenotype; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology / Q000235:genetics / Q000523:psychology; D012931:Social Environment; D012932:Social Facilitation; D012933:Social Identification; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic / Q000235:genetics / Q000523:psychology; D014430:Twins, Monozygotic / Q000235:genetics / Q000523:psychology