title: Tobacco use and friendship networks: a cross-sectional study among Brazilian adolescents.
abstract: OBJECTIVE
  To determine the prevalence of tobacco use and its association with types of friendship networks, socioeconomic status and gender among Brazilian adolescents.
  
  
  METHODS
  A cross-sectional study was carried out with a representative sample of 905 students aged 15 to 19 years. Information on social networks and tobacco use was collected by the self-administered questionnaire 'Alcohol, Smoking and Substance Involvement Screening Test" and the question "What is your most important group of close friends?'. Socioeconomic status was assessed using an area-based social vulnerability index and type of school. Multinomial logistic regression analysis was employed to test associations between tobacco use and the independent variables.
  
  
  RESULTS
  The overall prevalence of tobacco use was 18.9%. Female adolescents had 3.80-fold greater odds of reporting weekly to daily tobacco use compared to male adolescents. Participants who reported that their most important groups of close friends were from church had a lower risk of reporting weekly to daily tobacco use in comparison to those who reported that their best friends were from school.
  
  
  CONCLUSIONS
  The prevalence of tobacco use was high and was associated with school-based (as compared to church-based) friendship networks, female gender and higher area-level socioeconomic status.
authors.affiliation: Departamento de Odontopediatria e Ortodontia, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil, kellyoliva@ig.com.br.
authors.forename: Kelly Oliva
authors.initials: KO
authors.lastname: Jorge
authors.affiliation: Departamento de Clínica Patológica e Cirurgia Odontológica, Faculdade de Odontologia, Brasil.
authors.forename: Luís Otavio
authors.initials: LO
authors.lastname: Cota
authors.affiliation: Departamento de Odontologia Social e Preventiva, Faculdade de Odontologia, Brasil.
authors.forename: Efigênia Ferreira
authors.initials: EF
authors.lastname: e Ferreira
authors.affiliation: Departamento de Odontopediatria e Ortodontia, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil, kellyoliva@ig.com.br.
authors.forename: Miriam Pimenta
authors.initials: MP
authors.lastname: do Vale
authors.affiliation: Department of Society, Human Development, and Health, Harvard School of Public Health, United States.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kawachi
authors.affiliation: Departamento de Odontopediatria e Ortodontia, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil, kellyoliva@ig.com.br.
authors.forename: Patrícia Maria
authors.initials: PM
authors.lastname: Zarzar
mesh_terms: D000293:Adolescent; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D033062:Friends; D006801:Humans; D008297:Male; D015995:Prevalence; D012574:Schools; D012923:Social Class; D012944:Social Support; D064424:Tobacco Use / Q000453:epidemiology*; D055815:Young Adult