title: A pediatric twin study of brain morphometry.
abstract: BACKGROUND
  Longitudinal pediatric neuroimaging studies have demonstrated increasing volumes of white matter and regionally-specific inverted U shaped developmental trajectories of gray matter volumes during childhood and adolescence. Studies of monozygotic and dyzygotic twins during this developmental period allow exploration of genetic and non-genetic influences on these developmental trajectories.
  
  
  METHODS
  Magnetic resonance imaging brain scans were acquired on a pediatric sample of 90 monozygotic twin pairs, 38 same-sex dyzygotic twin pairs, and 158 unrelated typically developing singletons. Structural equation modeling was used to estimate the additive genetic, common environment, and unique environment effects, as well as age by heritability interactions, on measures of brain volumes from these images.
  
  
  RESULTS
  Consistent with previous adult studies, additive genetic effects accounted for a substantial portion of variability in nearly all brain regions with the notable exception of the cerebellum. Significant age by heritability interactions were observed with gray matter volumes showing a reduction in heritability with increasing age, while white matter volume heritability increased with greater age.
  
  
  CONCLUSIONS
  Understanding the relative contributions of genetic and nongenetic factors on developmental brain trajectories may have implications for better understanding brain-based disorders and typical cognitive development.
authors.affiliation: Child Psychiatry Branch, National Institute of Mental Health, Bethesda, MD, USA.
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Wallace
authors.forename: J
authors.initials: J
authors.lastname: Eric Schmitt
authors.forename: Rhoshel
authors.initials: R
authors.lastname: Lenroot
authors.forename: Essi
authors.initials: E
authors.lastname: Viding
authors.forename: Sarah
authors.initials: S
authors.lastname: Ordaz
authors.forename: Michael A
authors.initials: MA
authors.lastname: Rosenthal
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Molloy
authors.forename: Liv S
authors.initials: LS
authors.lastname: Clasen
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Kendler
authors.forename: Michael C
authors.initials: MC
authors.lastname: Neale
authors.forename: Jay N
authors.initials: JN
authors.lastname: Giedd
mesh_terms: D000293:Adolescent; D002540:Cerebral Cortex / Q000033:anatomy & histology*; D002648:Child; D002657:Child Development / Q000502:physiology*; D004777:Environment; D006801:Humans; D008279:Magnetic Resonance Imaging; D010372:Pediatrics / Q000295:instrumentation*; D010641:Phenotype; D014427:Twins