title: Amygdala responses to emotional faces in twins discordant or concordant for the risk for anxiety and depression.
abstract: BACKGROUND
  Functional brain imaging studies have shown deviant amygdala responses to emotional stimuli in subjects suffering from anxiety and depressive disorder, but both hyperactivity and hypoactivity compared to healthy controls have been reported. To account for these discrepant findings, we hypothesize that genetic and environmental risk factors differently impact on amygdala functioning.
  
  
  METHODS
  To test this hypothesis, we assessed amygdala responses to an emotional faces paradigm during functional magnetic resonance imaging in monozygotic twin pairs discordant for the risk of anxiety and depression (n=10 pairs) and in monozygotic twin pairs concordant for high (n=7 pairs) or low (n=15 pairs) risk for anxiety and depression.
  
  
  RESULTS
  Main effects (all faces vs. baseline) revealed robust bilateral amygdala activity across groups. In discordant twins, increased amygdala responses were found for negatively valenced stimuli (angry/anxious faces) in high-risk twins compared to their low-risk co-twins. In contrast, concordant high-risk pairs revealed blunted amygdala reactivity to both positive and negative faces compared with concordant low-risk pairs. Post-hoc analyses showed that these findings were independent of 5-HTTLPR genotype.
  
  
  CONCLUSIONS
  Our findings indicate amygdala hyperactivity in subjects who are at high risk for anxiety and depression through environmental factors and amygdala hypoactivity in those at risk mainly through genetic factors. We suggest that this result reflects a difference in baseline amygdala activation in these groups. Future imaging studies on anxiety and depression should aim to avoid admixture of subjects who are at genetic risk with those at risk due to environmental factors.
authors.affiliation: Department of Psychiatry, Vrije Universiteit medical center, Amsterdam, The Netherlands. spa.wolfensberger@vumc.nl
authors.forename: Saskia P A
authors.initials: SP
authors.lastname: Wolfensberger
authors.forename: Dick J
authors.initials: DJ
authors.lastname: Veltman
authors.forename: Witte J G
authors.initials: WJ
authors.lastname: Hoogendijk
authors.forename: Dorret I
authors.initials: DI
authors.lastname: Boomsma
authors.forename: Eco J C
authors.initials: EJ
authors.lastname: de Geus
mesh_terms: D000328:Adult; D000679:Amygdala / Q000502:physiology*; D001007:Anxiety / Q000209:etiology / Q000503:physiopathology*; D001931:Brain Mapping; D003863:Depression / Q000209:etiology / Q000503:physiopathology*; D004200:Diseases in Twins; D004644:Emotions / Q000502:physiology*; D005145:Face; D005149:Facial Expression; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D012307:Risk Factors; D014430:Twins, Monozygotic