Aggression and violent offenses are common amongst forensic psychiatric patients. Notably, research distinguishes two motivationally distinct dimension of aggression-instrumental and reactive aggression. Instrumental aggression comprises of appetitive, goal-directed aggressive acts, whereas reactive aggression consists of affective, defensive violence with both their biological basis remaining largely unknown. Childhood trauma and functional genetic polymorphisms in catecholamines converting enzymes, such as mono-amino-oxidase A (MAO-A) and catechol-o-methyltransferase (COMT) have been suggested to augment an aggressive behavioral response in adulthood. However, it warrants clarification if these factors influence one or both types of aggression. Furthermore, it remains elusive, if having a combination of unfavorable enzyme genotypes and childhood maltreatment further increases violent behavior. Hence, we set out to address these questions in the current study. First, analysis revealed an overall marginally increased frequency of the unfavorable MAO-A genotype in the test population. Second, each gene polymorphisms together with a traumatic childhood significantly increased the AFAS (Appetitive and Facilitative Aggression Scale) scores for both reactive and appetitive aggression. Third, having a combination of both disadvantageous genotypes and a negative childhood served as a minor positive predictor for increased reactive aggression, but had a strong influence on the joy of being aggressive.
Keywords: COMT; MAO-A; appetitive aggression; forensic patients; genetic polymorphism; reactive aggression.