title: Understanding genetic risk for aggression: clues from the brain's response to social exclusion.
abstract: BACKGROUND
  Although research indicates a relationship between the monoamine oxidase-A (MAOA) gene and aggression, the intervening neural and psychological mechanisms are unknown. Individuals with the low expression allele (MAOA-L) of a functional polymorphism in the MAOA gene might be prone to aggression because they are socially or emotionally hyposensitive and thus care less about harming others or because they are socially or emotionally hypersensitive and thus respond to negative social experiences with defensively aggressive behavior.
  
  
  METHODS
  We investigated the relationships between the MAOA polymorphism, trait aggression, trait interpersonal hypersensitivity, and neural responses to social exclusion in 32 healthy men and women.
  
  
  RESULTS
  The MAOA-L individuals (men and women) reported higher trait aggression than individuals with the high expression allele (MAOA-H). The MAOA-L individuals reported higher trait interpersonal hypersensitivity and showed greater dorsal anterior cingulate cortex (dACC) activity (associated with rejection-related distress) to social exclusion compared with MAOA-H individuals, consistent with a social hypersensitivity hypothesis. Moreover, the MAOA-aggression relationship was mediated by greater dACC reactivity to social exclusion, suggesting that MAOA might relate to aggression through socioemotional hypersensitivity.
  
  
  CONCLUSIONS
  These data suggest that the relationship between MAOA and aggression might be due to a heightened rather than a reduced sensitivity to negative socioemotional experiences like social rejection.
authors.affiliation: Department of Psychiatry & Biobehavioral Sciences, Cousins Center for Psychoneuroimmunology, Los Angeles, California 90095-7076, USA. neisenbe@ucla.edu
authors.forename: Naomi I
authors.initials: NI
authors.lastname: Eisenberger
authors.forename: Baldwin M
authors.initials: BM
authors.lastname: Way
authors.forename: Shelley E
authors.initials: SE
authors.lastname: Taylor
authors.forename: William T
authors.initials: WT
authors.lastname: Welch
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Lieberman
mesh_terms: D000328:Adult; D000374:Aggression / Q000502:physiology*; D000483:Alleles; D001923:Brain Chemistry / Q000235:genetics*; D002540:Cerebral Cortex / Q000502:physiology; D026661:Clinical Trials Data Monitoring Committees; D004644:Emotions / Q000502:physiology; D005260:Female; D005838:Genotype; D006801:Humans; D007398:Interpersonal Relations; D008279:Magnetic Resonance Imaging; D008297:Male; D011110:Polymorphism, Genetic / Q000235:genetics; D011581:Psychological Tests; D012306:Risk; D012931:Social Environment