Susan C. South

Environmental Adversity and Increasing Genetic Risk for Externalizing Disorders

CONTEXT Studies of gene-environment interplay in the development of psychiatric and substance use disorders are rapidly accumulating. However, few attempts have been made to integrate findings and to articulate general mechanisms of gene-environment influence in the emergence of psychopathology. OBJECTIVE To identify patterns of gene-environment interplay between externalizing disorders (antisocial behavior and substance use) and several environmental risk factors. DESIGN We used quantitative genetic models to examine how genetic and environmental risk for externalizing disorders changes as a function of environmental context. SETTING Participants were recruited from the community and took part in a daylong assessment at a university laboratory. PARTICIPANTS The sample consisted of 1315 male and female twin pairs participating in the assessment of the Minnesota Twin Family Study at age 17 years. MAIN OUTCOME MEASURES Multiple measures and informants were used to construct a composite of externalizing disorders and composite measures of 6 environmental risk factors, including academic achievement and engagement, antisocial and prosocial peer affiliations, mother-child and father-child relationship problems, and stressful life events. RESULTS A significant gene x environment interaction was detected between each environmental risk factor and externalizing such that greater environmental adversity was associated with increased genetic risk for externalizing. CONCLUSIONS In the context of environmental adversity, genetic factors become more important in the etiology of externalizing disorders. The consistency of the results further suggests a general mechanism of environmental influence on externalizing disorders regardless of the specific form of the environmental risk.

The Hierarchical Taxonomy of Psychopathology (HiTOP) : A Dimensional Alternative to Traditional Nosologies

The reliability and validity of traditional taxonomies are limited by arbitrary boundaries between psychopathology and normality, often unclear boundaries between disorders, frequent disorder co-occurrence, heterogeneity within disorders, and diagnostic instability. These taxonomies went beyond evidence available on the structure of psychopathology and were shaped by a variety of other considerations, which may explain the aforementioned shortcomings. The Hierarchical Taxonomy Of Psychopathology (HiTOP) model has emerged as a research effort to address these problems. It constructs psychopathological syndromes and their components/subtypes based on the observed covariation of symptoms, grouping related symptoms together and thus reducing heterogeneity. It also combines co-occurring syndromes into spectra, thereby mapping out comorbidity. Moreover, it characterizes these phenomena dimensionally, which addresses boundary problems and diagnostic instability. Here, we review the development of the HiTOP and the relevant evidence. The new classification already covers most forms of psychopathology. Dimensional measures have been developed to assess many of the identified components, syndromes, and spectra. Several domains of this model are ready for clinical and research applications. The HiTOP promises to improve research and clinical practice by addressing the aforementioned shortcomings of traditional nosologies. It also provides an effective way to summarize and convey information on risk factors, etiology, pathophysiology, phenomenology, illness course, and treatment response. This can greatly improve the utility of the diagnosis of mental disorders. The new classification remains a work in progress. However, it is developing rapidly and is poised to advance mental health research and care significantly as the relevant science matures.

Externalizing disorders: Cluster 5 of the proposed meta-structure for DSM-V and ICD-11

BACKGROUND The extant major psychiatric classifications DSM-IV and ICD-10 are purportedly atheoretical and largely descriptive. Although this achieves good reliability, the validity of a medical diagnosis is greatly enhanced by an understanding of the etiology. In an attempt to group mental disorders on the basis of etiology, five clusters have been proposed. We consider the validity of the fifth cluster, externalizing disorders, within this proposal. METHOD We reviewed the literature in relation to 11 validating criteria proposed by the Study Group of the DSM-V Task Force, in terms of the extent to which these criteria support the idea of a coherent externalizing spectrum of disorders. RESULTS This cluster distinguishes itself by the central role of disinhibitory personality in mental disorders spread throughout sections of the current classifications, including substance dependence, antisocial personality disorder and conduct disorder. Shared biomarkers, co-morbidity and course offer additional evidence for a valid cluster of externalizing disorders. CONCLUSION Externalizing disorders meet many of the salient criteria proposed by the Study Group of the DSM-V Task Force to suggest a classification cluster.

Contrasting prototypes and dimensions in the classification of personality pathology: evidence that dimensions, but not prototypes, are robust.

BACKGROUND DSM-5 may mark the shift from a categorical classification of personality pathology to a dimensional system. Although dimensional and categorical conceptualizations of personality pathology are often viewed as competing, it is possible to develop categories (prototypes) from combinations of dimensions. Robust prototypes could bridge dimensions and categories within a single classification system. METHOD To explore prototype structure and robustness, we used finite mixture modeling to identify empirically derived personality pathology prototypes within a large sample (n=8690) of individuals from four settings (clinical, college, community, and military), assessed using a dimensional measure of normal and abnormal personality traits, the Schedule for Nonadaptive and Adaptive Personality (SNAP). We then examined patterns of convergent and discriminant external validity for prototypes. Finally, we investigated the robustness of the dimensional structure of personality pathology. RESULTS The resulting prototypes were meaningful (externally valid) but non-robust (sample dependent). By contrast, factor analysis revealed that the dimensional structures underlying specific traits were highly robust across samples. CONCLUSIONS We interpret these results as further evidence of the fundamentally dimensional nature of an empirically based classification of personality pathology.

Marital quality moderates genetic and environmental influences on the internalizing spectrum.

Poor marital quality is a reliable correlate of internalizing problems, but the etiology of this association has yet to be examined. Marital distress may exert its influence by acting as a stressor that enables the expression of latent genetic risk for internalizing psychopathology. The authors examined this question using 379 twin pairs, assessed for marital quality, symptoms of major depression (MD), generalized anxiety disorder (GAD), panic attacks (PA), and neuroticism (N). A phenotypic factor analysis confirmed that one factor best accounted for the variance shared between MD, GAD, PA, and N. After accounting for genetic influences on the general Internalizing factor, there were residual genetic influences on N but no specific genetic influences on any other individual internalizing syndrome. The authors found overlap between the genetic influences on marital quality and the internalizing spectrum. Finally, biometrical moderation models revealed that genetic effects on the Internalizing factor increased as the marital quality deteriorated (marital quality high: h(2) = 0.05; marital quality low: h(2) = 0.29), suggesting that those with a genetic predisposition to internalizing syndromes may be more likely to express this predisposition in the context of a dissatisfying marriage.

Personality Disorder Symptoms and Marital Functioning

Pathological personality is strongly linked with interpersonal impairment, yet no study to date has examined the relationship between concurrent personality pathology and dysfunction in marriage--a relationship that most people find central to their lives. In a cross-sectional study of a community sample of married couples (N = 82), the authors used multilevel modeling to estimate the association of self- and spouse-reported symptoms of personality disorder (PD) with levels of marital satisfaction and verbal aggression and perpetration of physical violence. Inclusion of self- and spouse report of total PD symptoms resulted in improved model fit and greater variance explained, with much of the improvement coming after the addition of spouse report. The incremental validity of spouse report for several of the 10 PD scales was supported for marital satisfaction and verbal aggression, particularly for the Borderline and Dependent PD scales.

Factorial Invariance of the Dyadic Adjustment Scale across Gender

The Dyadic Adjustment Scale (DAS; G. B. Spanier, 1976) is the most widely used inventory of relationship satisfaction in the social sciences, yet the question of whether it is measuring the same concept in men and women has never been addressed. In the current study, the authors examined the factor structure of the DAS in a sample of 900 currently married couples who participated in the Minnesota Twin Family Study. Confirmatory factor analysis was applied to a second-order factor solution with Spaniers four factors (Dyadic Consensus, Dyadic Satisfaction, Dyadic Cohesion, Affectional Expression) loading on one higher order factor (Relationship Adjustment), to test for measurement invariance across gender. The second-order solution was relatively invariant across gender, even when taking into account the nonindependent nature of the data. This suggests that the best conceptualization of the DAS is one of a gender-invariant measure of marital adjustment with four distinct subfactors and that differences between men and women on any of these constructs can be interpreted by both clinicians and researchers as true mean differences rather than measurement bias.

Genetic and environmental influences on internalizing psychopathology vary as a function of economic status.

BACKGROUND Different theories of the link between socio-economic status (SES) and mental illness have been postulated. In particular, two theories of this association, social causation and social selection, differ in the implied causal pathway. The authors employ behavior genetic modeling to consider evidence for both social selection and social causation in the relationship between income variation and internalizing disorders. METHOD Behavior genetic modeling was used to estimate the presence of gene-environment interaction (GxE, social causation) in the presence of gene-environment correlation (rGE, social selection). Participants were members of a sample of 719 twin pairs from the Midlife in the United States study. Four internalizing (INT) syndromes were assessed: major depression (MD); generalized anxiety disorder (GAD); panic attacks (PA); neuroticism (N). SES was measured with total family household income. RESULTS One factor best accounted for the variance shared between MD, GAD, PA and N. The etiology of variation in INT changed from high to low levels of income, with unique environmental factors playing a larger role in INT variation at lower levels of income. Across levels of income, rGE between income and INT was modest (low income ra=0.39 to high income ra=0.54), implying a selection process operating through genetic effects linking lower income with INT psychopathology. CONCLUSIONS Findings support social causation by suggesting that low income contributes significantly to environmental variation in INT. Modest support was found for social selection, but should be extended using longitudinal designs. Effective interventions for internalizing psychopathology may differ depending on income.

Adolescent Personality Moderates Genetic and Environmental Influences on Relationships with Parents

In contrast with early theories of socialization that emphasized the role of parents in shaping their childrens personalities, recent empirical evidence suggests an evocative relationship between adolescent personality traits and the quality of the parent-adolescent relationship. Research using behavior genetic methods suggests that the association between personality and parenting is genetically mediated, such that the genetic effects on adolescent personality traits overlap with the genetic effects on parenting behavior. In the current study, the authors examined whether the etiology of this relationship might change depending on the adolescents personality. Biometrical moderation models were used to test for gene- environment interaction and correlation between personality traits and measures of conflict, regard, and involvement with parents in a sample of 2,452 adolescents (M age = 17.79 years). They found significant moderation of both positive and negative qualities of the parent-adolescent relationship, such that the genetic and environmental variance in relationship quality varied as functions of the adolescents levels of personality. These findings support the importance of adolescent personality in the development of the quality of the parent-adolescent relationship.

Understanding general and specific connections between psychopathology and marital distress: a model based approach.

Marital distress is linked to many types of mental disorders; however, no study to date has examined this link in the context of empirically based hierarchical models of psychopathology. There may be general associations between low levels of marital quality and broad groups of comorbid psychiatric disorders as well as links between marital adjustment and specific types of mental disorders. The authors examined this issue in a sample (N = 929 couples) of currently married couples from the Minnesota Twin Family Study who completed self-report measures of relationship adjustment and were also assessed for common mental disorders. Structural equation modeling indicated that (a) higher standing on latent factors of internalizing (INT) and externalizing (EXT) psychopathology was associated with lower standing on latent factors of general marital adjustment for both husbands and wives, (b) the magnitude of these effects was similar across husbands and wives, and (c) there were no residual associations between any specific mental disorder and overall relationship adjustment after controlling for the INT and EXT factors. These findings point to the utility of hierarchical models in understanding psychopathology and its correlates. Much of the link between mental disorder and marital distress operated at the level of broad spectrums of psychopathological variation (i.e., higher levels of marital distress were associated with disorder comorbidity), suggesting that the temperamental core of these spectrums contributes not only to symptoms of mental illness but to the behaviors that lead to impaired marital quality in adulthood.