title: Being bullied as an environmentally mediated contributing factor to children's internalizing problems: a study of twins discordant for victimization.
abstract: OBJECTIVE
  To test whether the experience of being bullied has an environmentally mediated effect on internalizing symptoms in young children.
  
  
  METHODS
  A genetically informative, longitudinal 1994-1995 birth cohort.
  
  
  METHODS
  A nationally representative sample from the United Kingdom.
  
  
  METHODS
  We examined 1116 twin pairs who are participants in the Environmental Risk Longitudinal Twin Study. Main Exposure The experience of being bullied between the ages of 7 and 9 years.
  
  
  METHODS
  Mothers' and teachers' reports of children's internalizing problems at 7 and 10 years of age.
  
  
  RESULTS
  Monozygotic twins who had been bullied had more internalizing symptoms (mean, 0.23; SD, 1.00) compared with their co-twin who had not been bullied (mean, -0.13; SD, 0.86), indicating that being bullied has an environmentally mediated effect on children's internalizing problems (beta, 0.36 [95% confidence interval (CI), 0.18-0.54]). This effect remained significant after controlling for preexisting internalizing problems (beta, 0.26 [95% CI, 0.09-0.44]).
  
  
  CONCLUSIONS
  Being bullied at a young age is an environmentally mediated contributing factor to children's internalizing problems. Intervention programs aimed at reducing bullying behavior in schools and in the community have the potential to influence children's early symptoms of mental health problems.
authors.affiliation: Medical Research Council Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Campus Box P080, De Crespigny Park, London SE5 8AF, England. l.arseneault@iop.kcl.ac.uk
authors.forename: Louise
authors.initials: L
authors.lastname: Arseneault
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Milne
authors.forename: Alan
authors.initials: A
authors.lastname: Taylor
authors.forename: Felicity
authors.initials: F
authors.lastname: Adams
authors.forename: Kira
authors.initials: K
authors.lastname: Delgado
authors.forename: Avshalom
authors.initials: A
authors.lastname: Caspi
authors.forename: Terrie E
authors.initials: TE
authors.lastname: Moffitt
mesh_terms: D000374:Aggression / Q000523:psychology*; D002648:Child; D002653:Child Behavior Disorders / Q000453:epidemiology / Q000523:psychology*; D019548:Crime Victims / Q000523:psychology*; D005260:Female; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D012042:Registries; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014430:Twins, Monozygotic; D006113:United Kingdom / Q000453:epidemiology