BACKGROUND: Antisocial personality disorder (ASPD) is characterised by elevated 
impulsive aggression and increased risk for criminal behaviour and 
incarceration. Deficient activity of the monoamine oxidase A (MAOA) gene is 
suggested to contribute to serotonergic system dysregulation strongly associated 
with impulsive aggression and antisocial criminality.
AIMS: To elucidate the role of epigenetic processes in altered MAOA expression 
and serotonin regulation in a population of incarcerated offenders with ASPD 
compared with a healthy non-incarcerated control population.
METHOD: Participants were 86 incarcerated participants with ASPD and 73 healthy 
controls. MAOA promoter methylation was compared between case and control 
groups. We explored the functional impact of MAOA promoter methylation on gene 
expression in vitro and blood 5-HT levels in a subset of the case group.
RESULTS: Results suggest that MAOA promoter hypermethylation is associated with 
ASPD and may contribute to downregulation of MAOA gene expression, as indicated 
by functional assays in vitro, and regression analysis with whole-blood 
serotonin levels in offenders with ASPD.
CONCLUSIONS: These results are consistent with prior literature suggesting MAOA 
and serotonergic dysregulation in antisocial populations. Our results offer the 
first evidence suggesting epigenetic mechanisms may contribute to MAOA 
dysregulation in antisocial offenders.