The Texas Twin Project

Socioeconomic position, racial/ethnic minority status, and other characteristics of the macro-environment may be important moderators of genetic influence on a wide array of psychosocial outcomes. Designed to maximize representation of low socioeconomic status families and racial/ethnic minorities, the Texas Twin Project is an ongoing study of school-age twins (preschool through 12th grade) enrolled in public schools in the Austin, Texas and Houston, Texas metropolitan areas. School rosters are used to identify twin families from a target population with sizable populations of African American (18%), Hispanic/Latino (48%), and non-Hispanic White (27%) children and adolescents, over half of whom meet US guidelines for classification as economically disadvantaged. Initial efforts have focused on a large-scale, family-based survey study involving both parent and child reports of personality, psychopathology, physical health, academic interests, parent-child relationships, and aspects of the home environment. In addition, the Texas Twin Project is the basis for an in-laboratory study of adolescent decision-making, delinquency, and substance use. Future directions include geographic expansion of the sample to the entire state of Texas (with a population of over 25 million) and genotyping of participating twins.

The hierarchical structure of childhood personality in five countries: continuity from early childhood to early adolescence

Childhood personality is a rapidly growing area of investigation within individual differences research. One understudied topic is the universality of the hierarchical structure of childhood personality. In the present investigation, parents rated the personality characteristics of 3,751 children from 5 countries and 4 age groups. The hierarchical structure of childhood personality was examined for 1-, 2-, 3-, 4-, and 5-factor models across country (Canada, China, Greece, Russia, and the United States) and age group (3-5, 6-8, 9-11, and 12-14 years of age). Many similarities were noted across both country and age. The Five-Factor Model was salient beginning in early childhood (ages 3-5). Deviations across groups and from adult findings are noted, including the prominent role of antagonism in childhood personality and the high covariation between Conscientiousness and intellect. Future directions, including the need for more explicit attempts to merge temperament and personality models, are discussed.

Parent informants for child personality: agreement, discrepancies, and clinical utility

A long-standing issue in child clinical research is the integration of various informants, but this topic has not been comprehensively applied to the domain of child personality. Mothers and fathers rated their children (N = 346) on personality traits and behavioral problems. Mother-father agreement was highest for Conscientiousness and lowest for Neuroticism and Agreeableness. Each parent's ratings added incremental variance in predicting behavioral problems, and mother-father discrepancy predicted internalizing problems. These results suggest that both parents should be used as informants in child personality assessment and discrepancies might reflect meaningful variance with clinical utility.

The hierarchical structure of the Dimensional Assessment of Personality Pathology (DAPP-BQ)

Hierarchical personality models have the potential to identify common and specific components of DSM-IV personality disorders (PDs), and may offer a solution for the re-tooling of personality pathology in future versions of the DSM. In this paper, we examined the hierarchical structure of the Dimensional Assessment of Personality Pathology-Basic Questionnaire (DAPP-BQ; Livesley & Jackson, 2009) and the capacity of various trait components at different levels to predict DSM-IV PD symptoms. Participants were 275 psychiatric outpatients and 365 undergraduate students. Goldberg's (2006) bass-ackwards method was used to investigate the hierarchical structure of the DAPP-BQ. The predictive capacity of hierarchy components was assessed. We found that Level 5 of the hierarchy enhanced the capacity of the DAPP-BQ for predicting DSM PD symptoms beyond a four-factor structure, particularly for borderline PD.

Shared genetic influences on negative emotionality and major depression/conduct disorder comorbidity

OBJECTIVE

To investigate whether genetic contributions to major depressive disorder and conduct disorder comorbidity are shared with genetic influences on negative emotionality.

METHOD

Primary caregivers of 2,022 same- and opposite-sex twin pairs 6 to 18 years of age comprised a population-based sample. Participants were randomly selected across five regions in Tennessee, with stratification by age and geographic location. Face-to-face structured interviews were conducted with the primary caregiver of a representative sample of twins.

RESULTS

After accounting for genetic influences on negative emotionality, genetic influences on major depressive disorder/conduct disorder comorbidity were nonsignficant, but only in male twins. Specifically, 19% of the variance in the two disorders was accounted for by genetic factors shared with negative emotionality in male twins. Although the full hypothesis could not be tested in female twins, 10% to 11% of the variance in the two disorders was also accounted for by genetic factors shared with negative emotionality. Common shared environmental and nonshared environmental influences were found for major depressive disorder/conduct disorder comorbidity in male and female twins.

CONCLUSIONS

Negative emotionality represents an important dispositional trait that may explain genetic influences on major depressive disorder/conduct disorder comorbidity, at least for boys. Models of major depressive disorder/conduct disorder comorbidity must simultaneously measure common and specific genetic and environmental factors for a full understanding of this phenomenon. Gender differences require specific research attention in dispositional factors and developmental progression.

Etiology and measurement of relational aggression: A multi-informant behavior genetic investigation

Although the study of relational aggression is gaining attention in the literature, little is known about the underlying causes of this behavior and the relative validity of various informants. These issues were addressed in a sample of 1,981 6- to 18-year-old twin pairs (36% female, 34% male, 30% opposite-sex). Relational aggression was assessed via maternal and self-report using a structured interview. Univariate models estimated genetic and environmental influences by informant and examined evidence for gender differences. A psychometric model combined data from both informants to estimate etiologic influences that were both common to the informants and informant specific. In both sexes, the latent variable reflecting the mother's and child's shared perception of the child's relational aggression was substantially influenced by both additive genetic (63%) and shared environmental (37%) influences, although this latent variable accounted for much greater variance in the maternal report (66%) than it did in the youth report (9%). In addition, informant-specific additive genetic and shared environmental influences were found only for the youth report, with all remaining variance in the mother's report attributed to nonshared environmental influences. Results are discussed in the context of measuring relational aggression and the importance of multiple informants.

Psychometrics of a self-report version of the Child and Adolescent Dispositions Scale

Lahey and Waldman (2003, 2005) proposed a model in which three dispositions-sympathetic response to others; negative emotional response to threat, frustration, and loss; and positive response to novelty and risk-transact with the environment to influence risk for conduct disorder (CD). To test this model, the Child and Adolescent Dispositions Scale (CADS) was developed to measure these dispositions using parent ratings of the child. Here we report psychometric evaluations of a parallel youth self-report version (CADS-Y). Exploratory factor analysis of CADS-Y items among 832 9- to 17-year-olds yielded a 3-factor structure that was consistent with the model and invariant across sex and informants. In 1,582 pairs of 9- to 17-year-old twins, confirmatory factor analyses supported the CADS-Y 3-factor model. Each CADS-Y dimension was associated with CD and related personality dimensions as predicted.

Personality in Middle Childhood: A Hierarchical Structure and Longitudinal Connections With Personality in Late Adolescence

Research on the structure of personality in middle childhood, while advancing, is still in the early stages of development. In this study, we employed a group of 1563 twins to elucidate the hierarchical structure of personality in middle childhood and provide connections to established personality traits in adult populations. Our results provide evidence for a higher-order structure of personality in middle childhood that maps on to recent findings in adult populations supporting hierarchical relationships among 2-, 3-, 4-, and 5-factor models of personality. In addition, primary higher-order personality traits rated by parents at age 11 showed substantial predictive validity for analogous traits rated by self at age 17. We discuss our results within the context of developing a convergent hierarchical taxonomy of personality in middle childhood and the importance of multiinformant investigations.

Evaluating models of the personality–psychopathology relationship in children and adolescents

Connections between personality traits and psychopathology in children and adolescents have frequently been reported in research studies. However, despite the occurrence of significant and systematic relationships between personality and mental disorders in childhood, a thorough understanding of the cause, nature, and implications of these relationships is lacking. In this paper, a comprehensive taxonomy of childhood personality is used to link research on children with that on adults, as well as provide a framework for discussing the personality-psychopathology relationship. Next, research on children and adolescents is integrated into various proposed models of the personality-psychopathology relationship. Finally, clinical implications and future directions are proposed for research on personality and psychopathology in children.

Symptom-based subfactors of DSM-defined conduct disorder: evidence for etiologic distinctions

Past research investigating the structure of conduct disorder (CD) symptoms has provided evidence of a phenotypic distinction between aggressive and rule-breaking subfactors of CD. However, evidence of etiologic distinctions between these subfactors has not been reported to date. In the current study, the authors investigated this issue in a sample of 1,151 male twins who were 17 years of age. The results indicate that aggressive and rule-breaking CD subfactors have both common and distinct etiologic influences, with shared environmental influences playing a significant role in rule-breaking behaviors. The authors discuss implications of these findings for the assessment and treatment of CD.

Progress and innovation: personality disorders and the vanguard of psychopathology research

Important progress in our understanding of the natural course of personality disorders (PDs) is documented in the articles for this special section. This progress could set the stage for ideas developed in the study of PDs to play a central role in research on psychopathology more broadly conceived. The Collaborative Longitudinal Personality Disorders Study (Skodol et al., this issue), the Children in the Community Study (Cohen, Crawford, Johnson, & Kasen, this issue), and the McLean Study of Adult Development (Zanarini, Frankenburg, Hennen, Reich, & Silk, this issue) reveal the importance of personality in understanding psychopathology, and point toward a dimensional approach to conceptualizing psychopathology that could also frame categorical clinical decision making processes.

Subfactors of DSM-IV conduct disorder: evidence and connections with syndromes from the Child Behavior Checklist

Is conduct disorder (CD) as defined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; American Psychiatric Association, 1994) a unitary entity, or do variants of CD exist? We addressed this question, using data collected from the parents of 1,669 Australian boys, aged 6-17. Parents were interviewed to assess DSM-IV Conduct Disorder (DSM-IV CD) criteria. Results revealed 2 subfactors of DSM-IV CD symptoms, made up of overt behaviors (e.g., initiating physical fights) and covert behaviors (e.g., stealing without confrontation). Ordinary least squares regressions showed the 2 CD subfactors to be significantly and uniquely predicted by Child Behavior Checklist (CBCL; T. M. Achenbach, 1991a, 1991b) syndromes labeled Aggressive Behavior and Delinquent Behavior, respectively. The results are discussed in terms of the utility of differentiating these 2 variants of CD in future editions of the DSM.

Structural models of comorbidity among common mental disorders: connections to chronic pain

Patterns of comorbidity among common mental disorders can be understood from the perspective of a model that regards mood, anxiety and somatization disorders as elements within an internalizing spectrum of disorder, and substance use and antisocial behavior disorders as elements within a separate externalizing spectrum of disorder. In this chapter, we evaluate the possibility of linking this model to literature on chronic pain. Evidence from psychosocial and biological perspectives points towards mechanisms that link chronic pain to internalizing disorders. Such evidence indicates that the internalizing-externalizing model may provide a useful framework for suggesting new directions for research on connections between chronic pain and mood, anxiety, and related disorders and traits.

Personality and psychopathology: working toward the bigger picture

There are systematic and meaningful links among normal and abnormal personality traits and Axis I and II constructs from the DSM. Nevertheless, much research in this area focuses on pairs of constructs (e.g., the link between personality traits and a specific Axis I disorder), rather than on the broader multivariate structure of the personality-psychopathology domain. We underscore the need for this broader perspective, a perspective that would transcend largely artificial boundaries between current constructs (e.g., normal and abnormal personality). We outline our approach to research from this perspective and we emphasize the internalizing (mood and anxiety) and externalizing (substance use and antisocial behavior) spectra as promising foci for initial research on the joint structure of personality and psychopathology.