title: A discordant monozygotic twin design shows blunted cortisol reactivity among bullied children.
abstract: OBJECTIVE
  Childhood adverse experiences are known to engender persistent changes in stress-related systems and brain structures involved in mood, cognition, and behavior in animal models. Uncertainty remains about the causal effect of early stressful experiences on physiological response to stress in human beings, as the impact of these experiences has rarely been investigated while controlling for both genetic and shared environmental influences.
  
  
  METHODS
  We tested whether bullying victimization, a repeated adverse experience in childhood, influences cortisol responses to a psychosocial stress test (PST) using a discordant monozygotic (MZ) twin design. Thirty pairs (43.3% males) of 12-year-old MZ twins discordant for bullying victimization were identified in the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally representative 1994-1995 cohort of families with twins.
  
  
  RESULTS
  Bullied and nonbullied MZ twins showed distinct patterns of cortisol secretion after the PST. Specifically, bullied twins exhibited a blunted cortisol response compared with their nonbullied MZ co-twins, who showed the expected increase. This difference in cortisol response to stress could not be attributed to children's genetic makeup, their familial environments, pre-existing and concomitant individual factors, or the perception of stress and emotional response to the PST.
  
  
  CONCLUSIONS
  Results from this natural experiment provide support for a causal effect of adverse childhood experiences on the neuroendocrine response to stress.
authors.affiliation: Institute of Psychiatry, King's College London, London.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Ouellet-Morin
authors.forename: Andrea
authors.initials: A
authors.lastname: Danese
authors.forename: Lucy
authors.initials: L
authors.lastname: Bowes
authors.forename: Sania
authors.initials: S
authors.lastname: Shakoor
authors.forename: Antony
authors.initials: A
authors.lastname: Ambler
authors.forename: Carmine M
authors.initials: CM
authors.lastname: Pariante
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Papadopoulos
authors.forename: Avshalom
authors.initials: A
authors.lastname: Caspi
authors.forename: Terrie E
authors.initials: TE
authors.lastname: Moffitt
authors.forename: Louise
authors.initials: L
authors.lastname: Arseneault
mesh_terms: D001143:Arousal / Q000235:genetics / Q000502:physiology; D058445:Bullying / Q000523:psychology*; D002648:Child; D015331:Cohort Studies; D019548:Crime Victims / Q000523:psychology; D004200:Diseases in Twins / Q000097:blood* / Q000235:genetics* / Q000523:psychology; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007389:Internal-External Control; D008137:Longitudinal Studies; D008297:Male; D009034:Mother-Child Relations; D012307:Risk Factors; D012931:Social Environment; D013315:Stress, Psychological / Q000150:complications; D014430:Twins, Monozygotic / Q000235:genetics* / Q000523:psychology; D006113:United Kingdom
chemical_list: D006854:Hydrocortisone