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It’s not my fault I am aggressive, they picked on me: How early peer relations affect DNA methylation and neurocognitive development in children

Periodic Reporting for period 3 - socio-bio interplay (It’s not my fault I am aggressive, they picked on me: How early peer relations affect DNA methylation and neurocognitive development in children)

Reporting period: 2018-03-01 to 2019-08-31

Each year, approximately 190,000 children in the Netherlands enter kindergarten or elementary school. These children enter a new social environment, the classroom, with new social interactions with teachers and age-matched peers. Most of these children will have positive social experiences, but 10-15% of children become rejected, victim of bullying, have few friends and have poor relations with teachers. Such experiences have been linked to aggression development in children, but we poorly understand how.
This project was set out to study how adverse social experiences in kindergarten and elementary school become embodied in the neurobiology of children, to explain aggression development. Specifically, the project aimed to understand how social experiences inflict aggression by (1) silencing genes underlying stress system responses, leading to impeded stress regulation, and by (2) affecting neurocognitive functions, thereby hindering children's self-regulation abilities.
Main objective 1:
Study the impact of elementary school social experiences on DNA methylation and cognitive development above and beyond possible genetic effects in monozygotic twins concordant/discordant on bully-victimization.
Progress till January 2018
Data from 196 monozygotic twin pairs are currently being collected. Data are collected at two time-points, when the twins are on average seven years old, and one year later, when the twins are on average 8 years old. Twins, classmates, and teachers are informants. Data will become available in 2018.

Main objective 2:
Study the cross-time influence of multiple adverse and protective social experiences with peers and teachers to test for possible cascading, accentuation and buffering between different social experiences, and test for sex-differences in these influences in a longitudinal observational study of children followed across elementary school.
Progress till January 2018
Data among 1000+ children attending mainstream elementary schools have been collected. Children have been assessed annually across the elementary school years (age 5 - 12 years). Teacher, peer, and self-report data on children's social relations and social experiences with teachers and classroom peers, and on children's psychopathology have been collected. Test scores of children's social decision making, working-memory, risk-taking, and behavioral inhibition were obtained annually. Three waves of DNA have also been collected, and DNA epigenetic analyses (EPIC array) are currently conducted. Data will become available in February 2018.

Main objective 3:
Study hypothesized stress- and self-regulatory variables that mediate the effects of altered DNA methylation and altered neurocognitive functions on aggressive responses. Children discordant on their social experiences in school will be tested in two lab-experimental studies.
Progress till January 2018
In study 1, 70 children (50% rejected) were tested in an fMRI study. In the fMRI experiement, children completed a dictator game, followed by a social exclusion task (Cyberball), followed by a second dictator game. Data are just available.
55 children (50% rejected) were invited to participate in the stress-lab study. Children's heart rate and cortisol concentrations were administered during the lab-assessment. Children first completed the BART-task, followed by a social exclusion experience. Children then completed the social decisions task (Hungry Donkey task). Data are just available.
Studying the impact of school social experiences on the neurobiology of children is crucial for our understanding of childhood aggression development. Approximately 15-30% of all children show aggression prior to elementary school, but only 5-10% become chronically aggressive. What is intriguing is that children who become chronically aggression do not differ from those who desist in aggression on their genetic or cognitive risk prior to entering elementary school. A crucial objective regarding aggression development is therefore to understand how despite similar levels of neurobiological risk prior to elementary school only some children develop into chronic aggression, while others show decreases in their aggression to low or absent levels by the end of elementary school. This project is set out to study the embodiment of adverse social experiences by shaping neurobiological, i.e. psychophysiological and neurocognitive processes underlying aggression development.