The contribution of a polygenic risk score to individual differences in aggressive behavior: The moderating and mediating roles of stressful events

Although aggression can be beneficial in certain situations (e.g. playing sports, self-defense), excessive and inappropriate aggression can lead to adverse physical and psychological health outcomes in both perpetrators and victims. Genetic susceptibility to negative environments can increase the likelihood of aggressive behavior in the context of situational risk factors. Low efficiency of serotonin neurotransmission and exposure to stress appear to play a prominent role in the etiology of aggressive behavior. A set of three studies assessed the contribution of polygenic risk (TPH2 rs4570625, SLC6A4 5-HTTLPR+rs25531, HTR1B rs13212041, MAOA uVNTR) to aggressive behavior, including alcohol-related aggression, in university students at varying reported levels of childhood stress (i.e. exposure to childhood trauma, lack of social support). Additionally, the mediating role of acute stress on the association between the polygenic risk score and aggression was examined using both self-report measures and experimental manipulation. It was expected that increased genetic susceptibility would predict higher aggressive behavior resulting from stress, and that the association would be greater as level of exposure to childhood stress increased. Hypotheses for the study were partially supported. Findings showed that individuals with higher genetic susceptibility (i.e. high polygenic risk score) reported engaging in more aggression if they reported experiencing higher levels of childhood trauma and reported engaging in less aggression if they reported experiencing lower levels of childhood trauma. In women only, higher genetic susceptibility and higher reported levels of childhood trauma also predicted more aggression indirectly via higher acute perceived stress. However, these results did not generalize to alcohol-related aggression. The pattern of results is consistent with the Differential Susceptibility Model based on a visual inspection and suggests that individuals with genetic risk who have experienced childhood trauma may benefit from intervention and prevention strategies. Because the association in women between the polygenic risk score and aggression was mediated by stress, intervention and prevention strategies that focus on teaching adaptive coping techniques may be particularly useful in reducing aggressive behavior in women that occurs as a result of stress