title: Comparison of Twin and Extended Pedigree Designs for Obtaining Heritability Estimates.
abstract: This study explores power assumptions relating to extended pedigree designs (EPD) and classical twin designs (CTD). We conducted statistical analyses to compare the power of the two designs for examining neuroimaging phenotypes, varying heritability and varying whether shared environmental variance is fixed or free. Results indicated that CTDs have more power to estimate heritability, with the exception of one condition: in EPDs, the power increases relative to CTDs when shared environmental variance contributes to sibling similarity only. We additionally show that assuming a priori that shared environmental effects play no role in a phenotype-as is commonly done in pedigree designs-can lead to substantially biased heritability estimates. General results indicate that both CTDs and EPDs obtain quite precise heritability estimates. Finally, we discuss methodological considerations relating to assumptions about age effects and shared environment.
authors.affiliation: Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University School of Medicine, Richmond, VA, 23219, USA, ardocherty@vcu.edu.
authors.forename: Anna R
authors.initials: AR
authors.lastname: Docherty
authors.forename: William S
authors.initials: WS
authors.lastname: Kremen
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Panizzon
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Prom-Wormley
authors.forename: Carol E
authors.initials: CE
authors.lastname: Franz
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lyons
authors.forename: Lindon J
authors.initials: LJ
authors.lastname: Eaves
authors.forename: Michael C
authors.initials: MC
authors.lastname: Neale
mesh_terms: D003198:Computer Simulation; D004777:Environment; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D015233:Models, Statistical; D010375:Pedigree; D010641:Phenotype; D019655:Quantitative Trait, Heritable; D012107:Research Design; D035781:Siblings; D018433:Twin Studies as Topic; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics