title: Genetic and environmental influences on cortical surface area and cortical thickness in bipolar disorder.
abstract: BACKGROUND
  The risk of developing bipolar disorder (BD) has been linked to structural brain abnormalities. The degree to which genes and environment influence the association of BD with cortical surface area remains to be elucidated. In this twin study, genetic and environmental contributions to the association between liability to develop BD and surface area, thickness and volume of the cortex were examined.
  
  
  METHODS
  The study cohort included 44 affected monozygotic (nine concordant, 12 discordant) and dizygotic (four concordant, 19 discordant) twin pairs, and seven twins from incomplete discordant monozygotic and dizygotic discordant twin pairs. In addition, 37 monozygotic and 24 dizygotic healthy control twin pairs, and six twins from incomplete monozygotic and dizygotic control pairs were included.
  
  
  RESULTS
  Genetic liability to develop BD was associated with a larger cortical surface in limbic and parietal regions, and a thicker cortex in central and parietal regions. Environmental factors related to BD were associated with larger medial frontal, parietal and limbic, and smaller orbitofrontal surfaces. Furthermore, thinner frontal, limbic and occipital cortex, and larger frontal and parietal, and smaller orbitofrontal volumes were also associated with environmental factors related to BD.
  
  
  CONCLUSIONS
  Our results suggest that unique environmental factors play a prominent role in driving the associations between liability to develop BD and cortical measures, particularly those involving cortical thickness. Further evaluation of their influence on the surface and thickness of the cortical mantle is recommended. In addition, cortical volume appeared to be primarily dependent on surface and not thickness.
authors: Brain Center Rudolf Magnus, University Medical Center Utrecht,Utrecht,The Netherlands.
authors: F
authors: F
authors: Bootsman
authors: Brain Center Rudolf Magnus, University Medical Center Utrecht,Utrecht,The Netherlands.
authors: R M
authors: RM
authors: Brouwer
authors: Brain Center Rudolf Magnus, University Medical Center Utrecht,Utrecht,The Netherlands.
authors: H G
authors: HG
authors: Schnack
authors: Julius Center, University Medical Center Utrecht,Utrecht,The Netherlands.
authors: G C M
authors: GC
authors: van Baal
authors: Brain Center Rudolf Magnus, University Medical Center Utrecht,Utrecht,The Netherlands.
authors: A C
authors: AC
authors: van der Schot
authors: Reinier van Arkel Group, 's-Hertogenbosch,The Netherlands.
authors: R
authors: R
authors: Vonk
authors: Brain Center Rudolf Magnus, University Medical Center Utrecht,Utrecht,The Netherlands.
authors: H E
authors: HE
authors: Hulshoff Pol
authors: Department of Psychiatry,University Medical Center Groningen,Groningen,The Netherlands.
authors: W A
authors: WA
authors: Nolen
authors: Brain Center Rudolf Magnus, University Medical Center Utrecht,Utrecht,The Netherlands.
authors: R S
authors: RS
authors: Kahn
authors: Brain Center Rudolf Magnus, University Medical Center Utrecht,Utrecht,The Netherlands.
authors: N E M
authors: NE
authors: van Haren
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001714:Bipolar Disorder / Q000235:genetics* / Q000503:physiopathology*; D002525:Cerebellar Cortex / Q000503:physiopathology*; D015331:Cohort Studies; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D007407:Interviews as Topic; D008032:Limbic System / Q000503:physiopathology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics; D055815:Young Adult