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December

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

DECEMBER 21, 2007

In the first research project of its kind to look at genes and the environmental effects on the role of bullying and victimisation, Harriet Ball, Louise Arseneault and colleagues in the Social, Genetic and Developmental Psychiatry Centre at the Institute of Psychiatry, at King's, have found there are strong genetic influences on being a victim, a bully, and being a bully-victim (a victim and a bully).

Genetic factors can influence a child’s individual characteristics in such a way as to increase their risk of becoming victimized, or being a bully. Additionally, but to a lesser extent environmental influences can affect bullying relationships.  The study shows that further research is needed to focus on the heritable characteristics within victims, as well as those within bullies, that lead to bullying relationships. 

In addition research is also needed to work out which heritable characteristics increase the risk of becoming a bully or a victim; and how we can modify the influence of these characteristics.  To reduce bullying, interventions should not just focus on bullies but on victims too, because characteristics of both parties contribute to the risk of being involved in bullying. 

The research paper: "Genetic and environmental influences on victims, bullies and bully-victims in childhood" is published in the January issue of the Journal of Child Psychology and Psychiatry, Volume 49, Issue 1 (January 2008) and on line by the journal from today, 21st December 2007.

SUMMARY
The researchers examined a nationally-representative cohort of 2,116 twins aged 9-10 years to understand the genetic and environmental influences on children’s risk of being a victim of bullying, being a bully, or being both a victim and a bully (referred to as bully-victims). In their sample, 12% of children had been severely bullied by others between the age of 9 and 10 years, 13% had frequently bullied others and 2.5% were both severely victimised and frequently bullied others (bully-victims). Knowing more about the factors that influence children’s risk of being involved in bullying is important because victims, bullies and especially bully-victims have elevated emotional and behavioural problems.

FINDINGS
Researchers found that, of the two influences being studied, genes were the most important factor influencing which children became victims and bullies: genetic influences explained 73% of children’s risk for being a victim and 61% of their risk for being a bully. Strong genetic influences on children’s risk of being a victim of bullying do not imply that victimisation is a personality trait, but merely acknowledges that genetic factors can influence children’s individual characteristics in such a way as to increase their risk of becoming victimised. These characteristics could include body weight, hair colour or clumsiness but also personality traits such as being timid or having difficulties controlling and understanding emotions. More research is needed to identify the heritable individual characteristics that are the links between genetics and being involved in bullying.

Environmental influences accounted for 27% of children’s risk for being a victim and 39% of their risk for being a bully. These environmental influences were unique to each twin in a pair, rather than shared by both children. These unique environmental influences, which impact upon each child differently, might include experiences at home or at school such as unique friendship groups and random factors and bad luck like being in the wrong place at the wrong time.

Moreover, genetic influences explained all the association between being a victim and being a bully (being a bully-victim).

IMPLICATIONS
a)      Finding strong genetic influences does not imply that children’s risk for being involved in bullying cannot be changed. There is scope for intervention by managing the heritable individual characteristics that can influence children’s involvement in bullying and this applies for victims as well as bullies. Interventions targeting those inherited characteristics could reduce the prevalence of children involved in bullying in the future.

b)      These findings do not direct the researchers at holding victims or bullies responsible for being involved in bullying. They rather indicate targets for intervening and elucidating the reasons why children get involved in bullying.

c)      The risk of being a victim is higher among bullies compared to children who do not bully others, and likewise, the risk of being a bully is higher among victims compared to children who are not bullied. People working with children known to be bullies or victims should consider the possibility that they are bully-victims and may be facing worse emotional and behavioural problems.

SUPPORTING DETAILS
Definition of terms: monozygostic/identical (MZ) twins: formed by splitting of the zygote and are thus genetically identical; dizygotic/fraternal (DZ) twins: formed by the release of two eggs by the mother, fertilised by two separate sperms from the father, and so are genetically equivalent to full siblings (50% of genetic material shared).

Twin studies: examining MZ and DZ twins reared together enables researchers to tease apart the influences of genes and environments. By looking at the extent to which pairs of MZ twins are more similar than pairs of DZ twins in terms of their bullying involvement, we can work out the size of the genetic influence on being involved in bullying

Victimisation: bullying is defined as repeated intentional harm taking place between people where there is a power differential between the bully and the victim (e.g. the bully is physically or psychologically stronger than the victim). Home visits were made to study families when the twins were 10 and mothers reported whether each of her twins had been bullied, at what age, and provided a description of events so that they could be confirmed as cases of victimisation by a bully. 

Bullying: mothers and teachers filled in a questionnaire when the twins were aged 10 (the Child Behaviour Check List), from which several items pertaining to bullying behaviours were used (e.g., “bullying or threatening people”, and “teases a lot”). 

Boys and girls: We found that the genetic and environmental influences were similar for boys and girls in our sample.

LIMITATIONS OF THE STUDY
•       Bullying experiences at a young age may be different for twins compared to singletons. However, the rates of victimisation and bullying we found in our sample of twins were similar to previous studies of singletons, suggesting our results can be generalised to children of the same age, not just twins.

•       This study reports on the genetic and environmental influences of being involved in bullying at one point in time only - at ages 9 and 10 years. The influences we found may differ for younger children and teenagers.

•       Because the children were young at the time of the study, we used adults’ reports of victimisation and bullying rather than children’s self-reports. We carried out a small study and we found good agreement between reports from children and adults, showing that adults can report on young children’s bullying experiences.

AUTHORS
Harriet A. Ball, Louise Arseneault, Alan Taylor, Barbara Maughan, Avshalom Caspi, Terrie E. Moffitt 

Collaborating universities: Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King’s College London, SE5 8AF, UK  and Departments of Psychology and Neuroscience, Psychiatry and Behavioural Sciences, and Institute for Genome Sciences and Policy, Duke University, Durham, USA

PRIMARY FUNDING AGENCIES
Medical Research Council (UK) 
Economic and Social Research Council (UK) 
Jacobs Foundation 
The British Academy 
The Nuffield Foundation

The JCPP is owned by The Association for Child and Adolescent Mental Health (ACAMH.)  For further information, please contact the ACAMH office, Tel: +44 (0)20 7403 7458 or Email: ingrid.king@acamh.org.uk.  Please note, the ACAMH offices are closed between Friday 21st December 2007 and Tuesday 2nd January 2008.

JCPP is published by Wiley-Blackwell on behalf of the Association for Child and Adolescent Mental Health.
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