Evidence for an Extended Externalizing Spectrum in Youth: Associations between Psychopathology, Personality, and Behavior Restricted; Files Only

Poore, Holly (Spring 2021)

Permanent URL: https://etd.library.emory.edu/concern/etds/1j92g8461?locale=en


Personality-psychopathology associations have long been documented, leading researchers to propose alternative models that seek to explain the mechanism of these associations. One such model, termed a spectrum model, posits that both constructs exist along the same continuum. Herein, I present three studies that examine evidence for an Externalizing Spectrum in youth using phenotypic (Study 1), quantitative genetic (Study 2), and molecular genetic analyses (Study 3). Studies 1 and 2 relied on a representative sample of twins and their siblings who are part of the Georgia Twin Registry (Npairs = 875, Ntotal = 2208). Study 3 relied on publicly available genome-wide association study (GWAS) summary statistics for externalizing disorders and related traits. In Study 1, we use Structural Equation Modeling and Item Response Theory to test the hypothesis that relevant personality and behavioral traits perform well as indicators of an Externalizing Spectrum model. We found evidence that traits reflecting narcissism, impulsivity, agreeableness, conscientiousness, behavioral disinhibition, and reactive, proactive, and relational aggression, load strongly with symptoms of externalizing disorders. We also found that many of these traits extend the levels of Externalizing captured, such that we were able to capture lower and higher levels of Externalizing relative to the symptom dimensions alone. In Study 2, we used quantitative genetic (i.e., twin) models to estimate the amount of etiological variance that these candidate traits share in common with Externalizing. We found that most candidate traits share substantial genetic, but not environmental, variance with externalizing symptom dimensions. Further, we found support for a model in which etiological influences on each disorder and trait predominantly exert their influence through a higher-order Externalizing factor that captures the genetic and environmental variance shared among its indicators, as well as genetic and environmental variance unique to each disorder and trait. Finally, in Study 3, we leveraged genetic correlations among externalizing disorders and related traits using GWAS summary statistics to test alternative models of the Externalizing Spectrum at the genomic level. We found support for the inclusion of aggression, agreeableness, risk tolerance, and number of sexual partners in the Externalizing spectrum. Taken together, our findings have several important implications. First, results from all studies support the existence of a broad Externalizing factor in youth that confers risk for many disorders and traits. Second, results from Studies 1 and 2 support the retention of specific facets of externalizing that represent unique variance not shared with other externalizing indicators. Finally, we found that the observed phenotypic associations between disorders and traits is due, at least in part, to shared etiological mechanisms, particularly common genetic influences. Overall, our findings support the existence of an Externalizing spectrum in youth, which should be the target of future studies examining the structure, nature, and treatment of externalizing problems in children and adolescents. 

Table of Contents

Table of Contents

General Introduction                                                                                                        1

Study 1: Examining Phenotypic Structural Models of the Externalizing Spectrum in Youth

           Abstract                                                                                                                     13

           Introduction                                                                                                             14

           Method                                                                                                                      21

           Results                                                                                                                       31

           Discussion                                                                                                                41

           Tables                                                                                                                        53

           Figures                                                                                                                      63

Study 2: Etiological Covariance Between Psychopathology and Personality Traits

           Abstract                                                                                                                    90

           Introduction                                                                                                            91

           Method                                                                                                                     95       

           Results                                                                                                                      99

           Discussion                                                                                                               102     

           Tables                                                                                                                       108

           Figures                                                                                                                     114

Study 3: Examining Evidence for an Externalizing Spectrum at the Genomic Level         

           Abstract                                                                                                                   119

           Introduction                                                                                                           120

           Method                                                                                                                    122

           Results                                                                                                                     127

           Discussion                                                                                                               129

           Tables                                                                                                                       132

           Figures                                                                                                                     137

General Discussion                                                                                                           151

References                                                                                                                          159

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