ESCAP 2015 Madrid State of the Art lecture

Bullying victimization and response to stress in children and adolescents

Louise Arseneault, Institute of Psychiatry, Psychology and Neuroscience at King’s College London, UK.

S4-02 – State of the Art Lecture, Sunday June 21st 2015


Background: Evidence from animal and human studies suggests that early adverse experiences such as maltreatment and bullying victimization have long-lasting effects on the hypothalamic-pituitary-adrenal (HPA) axis. However, uncertainty remains about the causal effect of these experiences in humans as no previous investigations controlled for genetic and shared-environmental influences. We tested whether bullying victimization affected cortisol reactivity using a discordant monozygotic (MZ) twin design and its impact on development.

Methods: Thirty pairs (43.3% males) of 12-year-old twins discordant for bullying victimization were identified in the E-Risk Study, a nationally-representative cohort of families with twins. We ascertained bullying using mothers’ and children’s reports, maltreatment using mothers’ reports and children’s behavioral problems using mothers’ and teachers’ reports.

Results: Bullied and non-bullied MZ twins showed distinct patterns of cortisol reactivity. Specifically, bullied twins exhibited blunted responses compared to their non-bullied MZ co-twins who showed the expected cortisol increase. This difference could not be attributed to children's genetic makeup, familial environments or pre-existing and concomitant individual factors. We subsequently showed in a larger sample (50.5% males; including discordant and non-discordant pairs) that maltreated/bullied children (n=64) also had lower cortisol responses in comparison to controls (n=126). Importantly, blunted responses were associated with more social and behavioral problems among maltreated/bullied children.

Conclusion: Results from this natural experiment support the enduring effects of early-life stress on cortisol reactivity. Moreover, our follow-up study showed that blunted responses may signal social and behavioral problems in maltreated/bullied children. The underlying role of DNA methylation will be discussed.