Violent offending is elevated among individuals with antisocial personality 
disorder (ASPD) and high psychopathic traits (PP). Morphological abnormalities 
of the amygdala and orbitofrontal cortex (OFC) are present in violent offenders, 
which may relate to the violence enacted by ASPD + PP. Among healthy males, 
monoamine oxidase-A (MAO-A) genetic variants linked to low in vitro 
transcription (MAOA-L) are associated with structural abnormalities of the 
amygdala and OFC. However, it is currently unknown whether amygdala and OFC 
morphology in ASPD relate to MAO-A genetic polymorphisms. We studied 18 ASPD 
males with a history of violent offending and 20 healthy male controls. Genomic 
DNA was extracted from peripheral leukocytes to determine MAO-A genetic 
polymorphisms. Subjects underwent a T1-weighted MRI anatomical brain scan that 
provided vertex-wise measures of amygdala shape and surface area and OFC 
cortical thickness. We found that ASPD + PP subjects with MAOA-L exhibited 
decreased surface area in the right basolateral amygdala nucleus and increased 
surface area in the right anterior cortical amygdaloid nucleus versus healthy 
MAOA-L carriers. This study is the first to describe genotype-related 
morphological differences of the amygdala in a population marked by high 
aggression. Deficits in emotional regulation that contribute to the violence of 
ASPD + PP may relate to morphological changes of the amygdala under genetic 
control.