Genetic vulnerability to bullying
04 June 2010
An international research team led by Dr Karen Sugden, at the Institute of Psychiatry (IoP), King’s College London (KCL) and Duke University, US reports new evidence that children who had experienced victimisation by bullies were more likely to develop emotional problems at 12 years old if they had one version of a genetic combination in the serotonin transporter gene.
Serotonin is a neurotransmitter (chemical messenger) involved in processes related to mood. The serotonin transporter re-cycles excess serotonin found between neurons, and regulates how neurons pass the message on.
Evidence from a study of 2,017 12-year old British children showed thatthe relationship between bullying victimisation and emotional problems depends on the victim’s serotonin transporter (5-HTT) gene. This region comes in two versions, the 'short' versus the 'long', and each person inherits two copies, one from each parent (a genotype). The study revealed that the 'short/short' genotype conferred vulnerability to bullying victimisation.
Researchers checked to see if the interaction between the gene and bullying predicted increases in emotional problems between age 5 (before the bullying was reported) and age 12 (after bullying). They found that short/short genotype children were at greater risk of developing emotional problems after frequent bullying victimisation than other children, regardless of their initial level of emotional problems at age 5.
To further confirm their findings the researchers compared emotional problems in twins who share both their genotype and family environment, but who differed in that one twin was bullied but their twin was not. In short/short twin pairs, the bullied twin had higher levels of emotional problems than their non-bullied twin.
Previous research has shown that short-carrying individuals are more likely to be threatened by and to avoid more dominant individuals, suggesting that short-carriers may be more sensitive to the threat of confrontation in the context of power imbalance (such as that experienced when bullied).
Dr Karen Sugden, a post-doctoral researcher at the IoP, said: 'This is a positive step forward and could instigate new intervention strategies for those children most at risk from the negative effects of bullying victimisation.'
In an interview with ‘Science News’, Professor of Social Behaviour and Development, Terrie Moffitt, at the IoP, said: 'School programmes to reduce bullying probably provide the greatest emotional benefits to genetically vulnerable children, but it's too early to say whether this research will lead to targeting genetically vulnerable children for specific school interventions.'
Participants made up 1,116 pairs of twins born in 1994 and 1995 in England and Wales. This birth cohort was initially assessed at age 5, and has been followed up at ages 7, 10 and most recently at 12 years, when more than 90% of the cohort (2,017 individual children) took part. The twins pairs were both monozygotic (identical; 55%) and dizygotic (fraternal; 45%), and all the pairs were the same sex.
‘Serotonin Transporter Gene Moderates the Development of Emotional Problems Among Children Following Bullying Victimization’ was published in this month’s Journal of the American Academy of Child and Adolescent Psychiatry, please follow the link: http://www.jaacap.com/article/S0890-8567(10)00284-4/abstract.