title: Bullying and weapon carrying: a meta-analysis.
abstract: OBJECTIVE
  Studies suggest that adolescents involved in bullying are more likely to carry weapons than their uninvolved peers.
  
  
  OBJECTIVE
  To use meta-analyses to determine whether victims, bullies, and bully-victims are more likely to carry weapons than uninvolved peers.
  
  
  METHODS
  PsycINFO, ERIC, MEDLINE, LILACS, EMBASE, and Dissertation Abstracts International were searched for relevant publications (1950 through January 2014). The reference list of a review article and reference lists of retrieved articles were checked for further relevant studies.
  
  
  METHODS
  Studies were included if they provided an effect size comparing the weapon carrying of adolescent victims, bullies, or bully-victims with that of uninvolved peers. Studies that included individuals older than 21 years were excluded, as were studies that focused on incarcerated youth or youth diagnosed as having a psychopathologic condition.
  
  
  METHODS
  Studies were coded independently by 2 of us. The agreement rate was 93%. Effect sizes were coded that compared victims, bullies, or bully-victims with uninvolved peers. Meta-analyses were based on 22 studies for victims (n = 257 179), 15 studies for bullies (n = 236 145), and 8 studies for bully-victims (n = 199 563).
  
  
  METHODS
  This study focused on weapon carrying among adolescents. Hypotheses were formulated before the study.
  
  
  RESULTS
  Victims (odds ratio, 1.97; 95% CI, 1.62-2.39), bullies (3.25; 2.72-3.89), and bully-victims (4.95; 3.77-6.50) were more likely to carry weapons than uninvolved peers. Analyses provided no indication of publication bias. Studies conducted in the United States found stronger relations between being a bully-victim and weapon carrying (odds ratio, 7.84; 95% CI, 6.02-10.21) than studies from other countries (3.62; 2.30-5.68; Q1 = 8.401; P = .004).
  
  
  CONCLUSIONS
  Involvement in bullying as a victim, bully, or bully-victim is related to weapon carrying.
authors.affiliation: Institute of Education and Child Studies, Leiden University, Leiden, the Netherlands.
authors.forename: Mitch
authors.initials: M
authors.lastname: van Geel
authors.affiliation: Institute of Education and Child Studies, Leiden University, Leiden, the Netherlands.
authors.forename: Paul
authors.initials: P
authors.lastname: Vedder
authors.affiliation: Hotelschool The Hague, Den Haag, the Netherlands.
authors.forename: Jenny
authors.initials: J
authors.lastname: Tanilon
mesh_terms: D000293:Adolescent; D058445:Bullying / Q000523:psychology*; D006801:Humans; D012307:Risk Factors; D054041:Weapons