Effects of MAOA genotype and childhood experiences of physical and emotional abuse on aggressive behavior in adulthood

A functional polymorphism in the monoamine oxidase A (MAOA) gene located on the X chromosome (Xp11.23-11.4) has earned the nickname “warrior gene” because of its association with antisocial behavior and delinquency. Previous findings on adults and adolescents have found some evidence that the MAOA gene moderates the impact of childhood abuse experiences on the risk of developing aggressive behavior. Thus far, however, attempts to replicate these findings have been mixed. The aims of the present study were to investigate whether the MAOA polymorphism affects aggressive behavior alone and in combination with childhood abuse experiences. We tried to replicate this using a sample of 1447 male and 2179 female Finnish twins and their siblings. In the present study, the Childhood Trauma Questionnaire and Aggression Questionnaire were used. There was a positive correlation between childhood abuse experiences and later aggressive behavior in adolescence or adulthood both for men and women. The results showed the effects of the 4-repeat allele of MAOA promoter polymorphism on physical aggressive behavior for women. It seems that there is an interaction between the 3-repeat allele of MAOA promoter polymorphism and emotional abuse experiences on aggressive behavior for women. In conclusions, this study, using a large population-based sample, found partial support for an interaction between MAOA genotype and childhood abuse experiences on aggressive behavior.