Ten-Year Rank-Order Stability of Personality Traits and Disorders in a Clinical Sample

Stability is a defining aspect of personality traits (Asendorpf, 1992; Caspi & Roberts, 1999; Funder, 1991) and issues of personality stability are central to questions about human nature (Roberts & Caspi, 2001). Retest correlations for core personality dispositions over fairly extended intervals are rarely lower than .50, and are often in the .80s (Ardelt, 2000; Roberts & Del Vecchio, 2000; Roberts & Mroczek, 2008; Ferguson, 2010; Lucas & Donnellen, 2011). Given this robust general finding, researchers have increasingly begun to focus on potential moderators of differential stability, such as the nature of the personality characteristics being examined (e.g., Ferguson, 2010). In this study, we compare ten-year stability coefficients for the scales of a normal trait questionnaire, a pathological trait questionnaire, and a personality disorder diagnostic interview in a clinical sample in order to evaluate the relative rank-order stability of normative and pathological personality dimensions. Based on the recent suggestion that differences between personality traits and disorders can be explained by lower dependability of personality disorder assessments (Chmielewski & Watson, 2009), we also examine the affects of differential dependability across assessment methods on personality stability estimates. The Stability of Normative and Pathological Personality Personality stability can depend on certain attributes of the constructs being examined. For example, researchers generally find that ratings of narrow affects such as anger or sadness are less stable than ratings of broad traits such as neuroticism (Vaidya, Gray, Haig, Mroczek, & Watson, 2008). This pattern may suggest that the tendency to experience negative emotions in general is stable over time, but the experience of specific negative emotions waxes and wanes according to interactions between dispositional propensities and environmental context. Other research indicates that personality disorders (PDs) are less rank-order stable than normative traits (Durbin & Klein, 2006; Morey et al., 2007), and in fact that normative trait stability is informative about PD symptomatology (Hopwood et al., 2009; Hopwood & Zanarini, 2010a; Wright, Pincus, & Lenzenweger, 2011). PD symptoms connote functional impairments that are thought to be influenced by environmental factors (e.g., social stressors) and to respond to psychosocial interventions (e.g., psychotherapy). To the extent that contexts change differentially across individuals over time, narrower and more specific behavioral manifestations of personality features that covary within these contexts may show reduced temporal consistency relative to broad and endogenous dispositions. This pattern parallels the separation of basic tendencies and characteristic adaptations in McCrae and Costa’s (1995 in McCrae and Costa’s (2003) Five-Factor Theory of personality. Basic tendencies to be more or less neurotic, extraverted, open, agreeable, and conscientious are thought to mature by early adulthood, at which point they remain relatively stable in the absence of extreme environmental changes throughout adulthood. Characteristic adaptations change in response to variability in the biological or social environment. From this perspective PD symptoms can be viewed as reflecting characteristic maladaptations, or maladjusted reactions to environmental contexts that are influenced by personality dispositions, previous experiences, and current contexts. These more behaviorally specific and contextual symptoms would thus be anticipated to be less stable over time than basic tendencies (Harkness & Lilienfeld, 1997; Harkness & McNulty, 2002). However, in a recent meta-analysis Ferguson (2010) compared stability effects from studies using broad versus narrow and normal versus pathological personality traits, and concluded that stability generally does not differ across these domains. Yet the authors of the only study used in Ferguson’s meta-analysis that directly compared retest correlations for traits and PDs in the same sample (Durbin & Klein, 2006) found that PD symptom counts were less stable than normal personality traits over ten years. This pattern was also observed in an article using data from the Collaborative Longitudinal Personality Disorders Study (CLPS) that did not contribute to Ferguson’s meta-analysis1. Specifically, Morey et al. (2007) observed mean two-year stability coefficients for Five Factor trait domains (.74) and facets (.67) that were somewhat larger than retest correlations for PD symptom counts (.59). Potential Effects of Reliability on Personality Stability One potential explanation for the discrepancy between the meta-analytic conclusion drawn by Ferguson (2010) and the results of these specific studies is that unlike Ferguson, neither Morey et al. (2007) nor Durbin and Klein (2006) corrected for short-term ‘dependability’ coefficients (retest correlations taken over a sufficiently short enough time interval that genuine trait change is deemed unlikely). Chmielewski and Watson (2009) compared short-term dependability in assessments of affects, normative traits, and schizotypal personality features and found that dependability tended to be lower for schizotypal features and affects than for normative traits. Correcting stability coefficients for dependability made the stabilities of affect measures more similar to those of trait measures. Chmielewski and Watson suggested based on these findings that correcting for dependability in PD ratings would close the gap between PD and trait stabilities as well. In particular, these authors argued that “transient error may have affected the findings of the Collaborative Longitudinal Study of Personality Disorders (CLPS), which documented high levels of change in PDs” (Chmielewski & Watson, 2009, p. 199). Although retest reliability data are available for the diagnostic interview in the CLPS sample (Zanarini et al., 2000), and dependability did not appreciably account for remission rates (i.e., mean-level stability) in Grilo et al. (2004), Chmielewski and Watson’s hypothesis has not yet been tested with respect to rank order stability, as we do in this study. Another methodological issue that could affect the differential stability of personality attributes involves the properties of self-report and interview assessment methods. Many clinicians and PD researchers have raised concerns about self-report questionnaires such as susceptibility to response bias (Huprich & Bornstein, 2007) and tend to favor diagnostic interviews for assessing personality pathology (Zimmerman et al., 1994). Conversely, most research on personality stability has been conducted using self-report questionnaires (Roberts & Del Vecchio, 2000). Because personality researchers interested in developmental issues such as stability prefer questionnaires and clinicians interested in the pathological consequences of personality value interviews, the issues of personality stability and normality versus pathology have sometimes been conflated. Indeed, Samuel et al. (2011) recently found, in the CLPS data, that PD constructs measured by self-report were more stable than PD constructs measured by diagnostic interview over two years, without controlling for dependability. This finding may suggest either that the interview method was less dependable than the questionnaire, or that the interview focused more on dynamic aspects of pathological personality whereas the questionnaire tapped more stable aspects. The Present Study To summarize, the similarity of retest stability estimates for normative traits, pathological traits, and PDs is important both for theoretical models of personality and personality pathology and also for applied personality assessment. However, several issues about the relative stability of these different aspects of personality have interacted in previous research in a manner that has generated a lack of clarity about possible moderators, rendering the relative effects of dependability, pathology, and behavioral specificity on personality stability over extended intervals unclear. To further evaluate these issues, we assess in this study the 10-year retest stability of normative traits, pathological traits, and PDs in the CLPS sample, controlling for dependability. This study is the first evaluation of 10-year differential stability of normative personality traits, pathological personality traits, and PD symptoms in a clinical sample, and the first direct comparison of differential stability across these assessment domains that controls for dependability.