Genetic and environmental influences on victims, bullies and bully-victims in childhood.

BACKGROUND Three groups of children are involved in bullying: victims, bullies and bully-victims who are both bullies and victims of bullying. Understanding the origins of these groups is important since they have elevated emotional and behavioural problems, especially the bully-victims. No research has examined the genetic and environmental influences on these social roles. METHOD Mother and teacher reports of victimisation and bullying were collected in a nationally representative cohort of 1,116 families with 10-year-old twins. Model-fitting was used to examine the relative influence of genetics and environments on the liability to be a victim, a bully or a bully-victim. RESULTS Twelve percent of children were severely bullied as victims, 13% were frequent bullies, and 2.5% were heavily involved as bully-victims. Genetic factors accounted for 73% of the variation in victimisation and 61% of the variation in bullying, with the remainder explained by environmental factors not shared between the twins. The covariation between victim and bully roles (r = .25), which characterises bully-victims, was accounted for by genetic factors only. Some genetic factors influenced both victimisation and bullying, although there were also genetic factors specific to each social role. CONCLUSIONS Children's genetic endowments, as well as their surrounding environments, influence which children become victims, bullies and bully-victims. Future research identifying mediating characteristics that link the genetic and environmental influences to these social roles could provide targets for intervention.