Scientists are discovering more and more information about the way in which people's genes and environment interact to affect their health. A study of 78 girls by researchers at Stanford University in Palo Alto, California looked into the links between bullying, depression and a variation in a gene called 5-HTTLPR. Between 20-40% of children report bullying of some kind and 3-8% of children report frequent victimization. Bullying has been linked to depression, anxiety, loneliness and low self-esteem and girls are both more likely to suffer from it and to be more severely affected by it while variations in the gene 5-HTTLPR have been linked to an increased vulnerability to depression. So, the study asked the children about their mental health and whether they had been bullied and also tested them to see which variation in the gene they had. The researchers found that the genetic variation did not influence the children's levels of depression on its own. However, of the girls who had been bullied only those with the genetic variation were significantly more likely to develop depression.
Benjet, Corina, Thompson, Renee J. and Gotlib, Ian H. - 5-HTTLPR moderates the effect of relational peer victimization on depressive symptoms in adolescent girls Journal of Child Psychology and Psychiatry February 2010, 51(2), 173-179