Background and Objectives: From a gene-by-environment perspective, parenting in interaction with the polymorphism in the Monoamine oxidase A (MAOA) gene (MAOA-uVNTR) might also be associated with increased callous-unemotional traits (CU) in preschoolers. MAOA-uVNTR results in differential enzyme activity, so that high-activity alleles (MAOA-H) are linked to reduced dopamine, serotonin, and norepinephrine availability in comparison to low-activity allele (MAOA-L). As MAOA-uVNTR has been previously described to moderate the relationship between childhood parental maltreatment and aggressive and antisocial behavior, it may also play a role in CU traits etiology
