title: Do episodes of peer victimization trigger physical injury? A case-crossover study of Swedish school children.
abstract: OBJECTIVE
  The aim of this study was to investigate how long the effect of peer victimization on the occurrence of physical injury lasts and whether the effect varies according to how frequently an injured child is victimized.
  
  
  METHODS
  A case-crossover design was employed. Children aged 10-15 years residing in Stockholm County during two consecutive school years were eligible as cases. Further inclusion criteria were that the children had been hospitalized or called back for a medical check-up due to a physical injury. Information on children's exposure to peer victimization at school was gathered in interviews, and on their social characteristics through a questionnaire filled in by parents. A total of 575 children were included.
  
  
  RESULTS
  Our analyses show that there is an increase in risk of unintentional injury after an episode of peer victimization shortly after the end of exposure to victimization (RR = 5.5) but not thereafter. The risk is substantially higher among children seldom victimized (RR = 49.9) than among those victimized on a more regular basis (RR = 2.5). The extent to which family social circumstances modify the risk is difficult to establish from the material at hand.
  
  
  CONCLUSIONS
  Peer victimization may trigger the occurrence of unintentional injuries in childhood and the effect is short lasting. The results need to be replicated and special attention should be given to separating lesson time from break time to avoid confounding by time of day.
authors.affiliation: Karolinska Institutet, Department of Public Health Sciences Division of Social Medicine, SE-171 76 Stockholm, Sweden. karin.engstrom@phs.ki.se
authors.forename: Karin
authors.initials: K
authors.lastname: Engström
authors.forename: Johan
authors.initials: J
authors.lastname: Hallqvist
authors.forename: Jette
authors.initials: J
authors.lastname: Möller
authors.forename: Lucie
authors.initials: L
authors.lastname: Laflamme
mesh_terms: D000293:Adolescent; D002648:Child; D019548:Crime Victims / Q000523:psychology / Q000706:statistics & numerical data; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D012307:Risk Factors; D012574:Schools; D012919:Social Behavior; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D013548:Sweden; D013997:Time Factors; D014947:Wounds and Injuries / Q000175:diagnosis / Q000209:etiology*