A taxonomic reconceptualization of personality disorders: Trait dimensions and level of dysfunction

Scriptie/masterproef: Doctoral Thesis


This dissertation was shaped in the midst of the transition between DSM-IV and DSM-5. Four years ago, when this research project was set in motion, no specific plans were out yet about how DSM-5 would look like. Many papers were written at that time, setting out research priorities for the next edition of the diagnostic manual (Clark, 2007; Krueger, Skodol, Livesley, Shrout, & Huang, 2007; Widiger, Simonsen, Krueger, Livesley, & Verheul, 2005), but no decisions had been made so far.
The purpose of this dissertation was not necessarily to contribute to the development of DSM-5 as such, but rather to participate to the broader scientific debate about the description, assessment, and classification of PDs that has been held in the context of this development, and hopefully to make a modest contribution to the expanding knowledge about the taxonomic nature of PDs.
As the title reveals, this dissertation mainly focuses on two taxonomic issues that have received the most attention in the run-up to DSM-5, being the implementation of an empirically supported dimensional trait model, and the necessity for a clearer articulation of functional impairments that are deemed central to the diagnosis of PD. This dissertation reports on four empirical studies that all addressed one or both of these topics, as well as a number of related side issues, using various methods and perspectives.
The first study (Chapter 2) investigated whether PDs are properly described as distinct categories falling neatly into three higher-order clusters, as it is implied by the current DSM-IV Axis II format, or whether they are better described by a set of shared underlying dimensions, which would be more consistent with a dimensional conceptualization. Structural equation modeling was used to test the categorical three-cluster configuration of DSM-IV's Axis II against an alternative dimensional four-factor structure that was based on a recent empirical meta-analysis (O'Connor, 2005), and that also corresponded to the consensus structure identified through a large-scale literature review (Widiger & Simonsen, 2005). Subsequently, the best fitting model was subjected to a multi-group confirmatory
factor analysis in order to test its generalizability across clinical and non-clinical samples.
In the search for an optimal dimensional model to accommodate PD symptoms, it has often been suggested to integrate Axis II with a dimensional model of general personality structure, like the Five-Factor Model (FFM; Clark, 2007; Widiger & Simonsen, 2005). However, it was also argued that its implementation would only be successful if the model would indeed be accepted and employed by clinicians. To facilitate a smooth transition, it was advised that if a dimensional model would be adopted, it should also enable clinicians to recover the traditional PD diagnoses (e.g., Krueger et al., 2007). The purpose of the second study (Chapter 3) was therefore to examine the ability of FFM-based prototypes to reproduce specific DSM-IV PD constructs, by means of a simple count technique developed by Miller, Bagby, Pilkonis, Reynolds, & Lynam (2005).
Because of the increasing awareness that personality traits alone were insufficient to cover all variation in PD symptoms, the third study (Chapter 4) was devoted to investigate the possible incremental contribution of a functional impairment measure to the prediction of specific PDs, using the Severity Indices for Personality Problems (SIPP-118; Verheul et al., 2008) as a starting point. First, the structure of the SIPP-118 was examined using a combination of exploratory and confirmatory factor analysis. The nature of the resulting subfactors was further examined by validating them against the traditional DSM-IV PD constructs, and against the general trait dimensions of the FFM. Finally, hierarchical regression analysis was used to determine the incremental validity of the SIPP-118 versus the FFM domains in predicting specific PDs.
An important discussion regarding the implementation of a dimensional trait model into the classification of PDs pertains to whether general or pathological personality traits would be better suited for this purpose, and which of both would provide more incremental information alongside an account of functional impairments (e.g., Hopwood, 2011). Whereas the previous chapter discussed the incremental validity of general personality traits beyond functional impairments, the fourth and last study (Chapter 5) focused on the incremental validity of pathological traits, as assessed by the Dimensional Assessment of Personality Pathology - Basic Questionnaire (DAPP-BQ; Livesley & Jackson, 2009). In addition, succeeding levels of the DAPP-BQ hierarchy (containing an increasing number of trait components) were considered in order to find an optimal balance between comprehensiveness and parsimony. In discussing and interpreting the results of this study, particular attention was paid to the issue of clinical utility (cf. Verheul, 2005).
The final Chapter 6 provides an integration of the major findings of these four studies. Moreover, the results are discussed from a broader perspective, and evaluated against the most recent proposals for DSM-5 (APA, 2012). Finally, an attempt is made to formulate some general conclusions, and to offer directions for future research.
Datum Prijs17 sep 2012
BegeleiderGina Rossi (Promotor), Joeri Hofmans (Jury), Eva Dierckx (Jury), Christiaan Schotte (Jury), Laurence Claes (Jury), Joost Hutsebaut (Jury) & Filip De Fruyt (Co-promotor)

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