Moderating effect of gender and MAOA genotype on aggression and violence

Abstract

Introduction: Biological sex contributes to aggression, but there are other factors, like gender and genes, which have also proven to contribute to this behavior. Gender is defined as the stereotyped characteristics of each sex, but currently four gender identities have been stated: androgynous, instrumental, expressive and undifferentiated. MAOA gene has been more often related to aggression, particularly the low variant (MAOAL) of the MAOA-uVNTR polymorphism. Objective: This study investigated whether there was an interaction between gender and MAOA genotype on aggression. Method: 292 healthy undergraduates were assessed using an aggression questionnaire (AQ) and an inventory of gender traits (EDAIE). The genotyping technique was employed to obtain the students’ MAOA genotype. Main and interaction effects split by sex were analyzed by two-way MANOVAs. Results: Androgynous traits had an effect on verbal aggression, anger, hostility and total aggression in males and females; while instrumental traits had an effect on physical aggression in males. MAOAH genotype had an effect on hostility in males; and MAOALH genotype on verbal aggression in females. Finally, a gender by MAOA-uVNTR interaction was observed on anger and total aggression in males. Conclusions: Males are more likely to show anger and aggression when the predisposing genetic and environmental factors interact. Androgynous identity seems to lead to general aggression in both sexes; while instrumental identity to physical aggression just in males. On the other hand, undifferentiated identity apparently leads to less aggression. These findings shed light on factors that could be initial indicators for future violent behavior.

Keywords

• Biological sex
• Gender
• Monoamine oxidase A
• Aggression
• Violence