| The aim of this dissertation study was to investigate the best models for estimating genetic and environmental influences on child externalizing behavior in multivariate multi-rater twin research. Empirical data were analyzed for a sample of 605 twin pairs (age 9-10), drawn from a twin study of risk factors for antisocial behavior at the University of Southern California (USC). The twins were rated by both caregivers and teachers on several aspects of externalizing behavior using three widely used instruments: symptoms for Attention Deficit Hyperactivity Disorder (ADHD) using the ADHD module in the Diagnostic Interview Schedule for Children (DISC-IV), aggressive behaviors using the Reactive and Proactive Aggression Questionnaire (RPQ), and Child Behavior Checklist Externalizing (CBCL) behavior problems. Six competing multi-trait multi-rater genetic models were fitted and the best fitting model was found to be the "general factor and correlated raters model", which include one common ADHD factor shared by all measurements and two oblique rater factors -- represented mainly by individual rater's view on aggression and delinquency. In terms of rater effects, mother reports were found to be more reliable, while teachers has less ability to distinguish different forms of externalizing behavior. This study also employed a Monte Carlo simulation to evaluate the power and parameter estimates of the "one common and two correlated rater factors model". Reasonable power and sufficient precision of parameter estimates were obtained at this sample size. All analyses for this dissertation were conducted in the Mplus software. |
