Comparing criterion- and trait-based personality disorder diagnoses in DSM-5.

Substantial evidence has accumulated showing both the limitations of the DSM-IV classification system for personality disorder (PD) as well as the advantages of understanding PD from a trait-dimensional perspective (e.g., Clark, 2007; Livesley, 2007; Trull & Durrett, 2005; Widiger & Samuel, 2005; Widiger & Trull, 2007). Despite these advances, the official PD classification remains unchanged in the revised Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association [APA], 2013). However, the Personality and PD workgroup proposed an alternative hybrid PD classification system that combines both dimensional and categorical elements, reflecting a compromise between those favoring a fully trait-based system (e.g., Clark, 2007; Widiger & Simonsen, 2005) and those favoring the polythetic categorical system embodied in the official nosology since 1980 (e.g., Gunderson, 2010; Zimmerman, 2012). To spur research into this alternative, DSM-5 lists the hybrid approach in Section III, but relatively little is known about how Section III PDs compare to their traditional counterparts. Thus, our principal aim was to compare the trait-based elements of the alternative approach to the criterion-based elements of the traditional PD classification system in terms of diagnostic validity and diagnosis rates. The Section III approach retains six of the ten traditional PDs—antisocial, avoidant, borderline, narcissistic, obsessive-compulsive, and schizotypal PDs. PDs are conceptualized as significant impairments in personality functioning coupled with pathological personality traits that are assessed across seven diagnostic criteria (APA, 2013). Criterion A evaluates personality functioning, comprising self and interpersonal impairments unique to each PD. Criterion B includes 25 personality traits—nested within five broad domains (negative affect, detachment, antagonism, disinhibition, and psychoticism)—that can be present in pre-specified configurations associated with each retained PD or in idiosyncratic configurations (i.e., PD trait-specified [PD-TS]). For example, a diagnosis of borderline PD requires at least four of the seven specified traits—anxiousness, depressivity, emotional lability, hostility, impulsivity, risk taking, and separation insecurity—with either impulsivity, risk taking, or hostility required. Criteria C to G include inclusion and exclusion criteria similar to the official system. Given the novelty of the Section III approach, relatively little has been published evaluating its utility and functioning vis-a-vis the official criterion-based model. However, two recent papers reported limited support for the particular trait-to-PD mappings suggested in Section III (Few et al, 2013; Hopwood et al. 2012). In both cases, although evidence showed that the Section III traits generally predicted official PD criterion counts, the specified trait-to-PD relations showed limited specificity, with (a) non-specified traits sometimes adding significantly to the prediction of certain PDs, and (b) specified traits often relating to multiple PDs. Although the non-specificity of traits is not surprising given the known patterns of comorbidity among the traditional PDs, these findings nonetheless raise important questions about the adequacy of the Section III trait configurations. Moreover, inconsistencies across the studies suggest that additional work is needed before strong conclusions are possible regarding how best to map PD traits onto traditional PDs. A related question not adequately addressed in Section III is the clinical threshold required for traits, which has important diagnostic implications. Notably, no specific thresholds are provided in Section III, except that trait elevation could be assessed by comparison to “population norms and/or clinical judgment” (p. 774; APA, 2013); the use of normative samples also has been suggested previously as a means of interpreting trait scores via standardized T-scores (Miller, 2012). Samuel et al. (2013) recently studied the impact of the proposed clinical thresholds on PD diagnosis rates in a large sample of undergraduates. Using norms reported by Krueger et al. (2012), Samuel et al. reported markedly lower diagnosis rates for trait-based diagnoses relative to the traditional criterion-based diagnoses. Although provocative, Samuel et al.'s data were collected in undergraduates; extension to patient samples is needed to study the generalizability of their results to more ecologically valid samples. Although the use of trait configurations as a dimensional bridge to the traditional criterion-based approach is not a new practice (e.g., Miller, 2012), an issue in need of further study is the extent of classification convergence across models. Morey and Skodol (2013) examined classification convergence through mental health clinicians who rated a prior patient using both the trait- and criterion-based models. Results showed general support for classification convergence, with correlations between DSM-5 and DSM-IV criterion counts yielding a Mdn correlation of .75. However, Morey and Skodol's approach was limited to clinician reports of patient symptomatology. A study reporting Section III diagnosis estimates and classification convergence from the patient perspective would meaningfully extend the literature. In sum, more work is needed to improve our understanding of inter-model convergence and diagnosis rates across PD classification approaches, with the aim of informing future revisions to PD nosology. As such, the goals of the present study were to study (a) how strongly Section III PD traits predict traditional PD criterion counts, (b) whether any non-specified PD trait incrementally predict PD criterion counts, and (c) Section III diagnosis rates in a large psychiatric sample.