title: Intrapair differences in hippocampal volume in monozygotic twins discordant for the risk for anxiety and depression.
abstract: BACKGROUND
  Current biological psychiatric models assume that genetic and environmental risk factors for anxiety and depression act on the same brain structures.
  
  
  METHODS
  To test this assumption, we assessed brain anatomy by using optimized voxel-based morphometry on magnetic resonance images obtained in monozygotic twin pairs who were discordant for the risk of anxiety and depression (n = 10 pairs) and in monozygotic twin pairs who were concordant for high (n = 7 pairs) or low (n = 15 pairs) risk for anxiety and depression.
  
  
  RESULTS
  We observed volume reductions in the temporal lobe, most notably in the left posterior hippocampal region in subjects at high risk for anxiety and depression, but exclusively in the intrapair comparison of discordant monozygotic twins. Because monozygotic twins are genetically identical, any discordance in their risk for anxiety and depression and hippocampal volume must arise from differential exposure to environmental influences. A group comparison between pairs concordant for low or high risk, which is more likely to reflect differences in genetic vulnerability, did not show reduced temporal-lobe and posterior hippocampal volumes in the pairs at high risk for anxiety and depression.
  
  
  CONCLUSIONS
  This pattern of results suggests that damage to temporal-lobe structures may be specific to an environmentally driven etiology of anxiety and depression.
authors.affiliation: Department of Biological Psychology, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands. eco@psy.vu.nl
authors.forename: Eco J C
authors.initials: EJ
authors.lastname: de Geus
authors.forename: Dennis
authors.initials: D
authors.lastname: van't Ent
authors.forename: Saskia P A
authors.initials: SP
authors.lastname: Wolfensberger
authors.forename: Peter
authors.initials: P
authors.lastname: Heutink
authors.forename: Witte J G
authors.initials: WJ
authors.lastname: Hoogendijk
authors.forename: Dorret I
authors.initials: DI
authors.lastname: Boomsma
authors.forename: Dick J
authors.initials: DJ
authors.lastname: Veltman
mesh_terms: D000293:Adolescent; D000328:Adult; D001007:Anxiety / Q000473:pathology*; D001921:Brain / Q000473:pathology; D003863:Depression / Q000473:pathology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D007361:Intelligence Tests; D008019:Life Style; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009497:Neurotic Disorders / Q000473:pathology; D010290:Parents; D012306:Risk; D012959:Socioeconomic Factors; D014430:Twins, Monozygotic