The spectrum of personality pathologies: zooming in on transdiagnostic dimensionality and operationalization in time-limited practice

Categorical personality disorder (PD) models have been rejected in favor of alternative
dimensional approaches by the DSM-5 Alternative Model for Personality Disorder (AMPD) in
and the ICD-11 classification. This has resulted in numerous studies testing the empirical
validity of the DSM-5 AMPD and ICD-11 approaches, including transdiagnostic indicators.
While well-validated self-reports support the operationalization of these dimensional
approaches, (semi)-structured interviews are considered the gold standard for the assessment
of PD. However, given the time constraints in clinical practice, there is a need to identify core
dimensions of personality pathology to get directly to the essence of PD.
Therefore, the present thesis focuses on the empirical foundation of three aspects of
dimensional PD approaches. First, we sought to examine the impact and transdiagnostic
overlap between potential personality pathologies and other mental disorders, e.g.,
somatization. Therefore, we conducted a systematic literature search to identify and synthesize
the evidence of convergence between personality dysfunctions and somatization disorder.
Additionally, existing concepts of somatization were crucially reflected in the context of the
DSM-5 AMPD (Study I). Second, we focused on the operationalization of personality
functioning according to DSM-5 AMPD. Therefore, we translated and evaluated the
psychometric properties of a self-report questionnaire – the Self and Interpersonal Functioning
Scale (SIFS). We then conducted and analyzed a large multi-method dataset from different
non-clinical and clinical samples and evaluated the structure, reliability, validity, and loading
pattern of the SIFS (Study II). Third, we sought to evaluate core dimensions of personality
dysfunction that can provide clinical approximation of the personality dysfunction severity in
time-limited practice. To this end, we used the data of a multi-method design consisting of
well-validated (semi-)structured interview and self-report ratings of personality functioning,
personality organization, and personality structure to calculate a latent method-adjusted general
factor of personality dysfunction severity (g-PDS; Study III).
Study I showed that PDs and personality pathologies are in fact often comorbid in
subjects suffering from somatization. Whereas categorical PD diagnosis models revealed
unspecific results, dimensional PD diagnostic approaches showed high associations with
somatization in the following personality dimensions: pathologies of the self, negative
affectivity harm avoidance, and self-defeating traits. This underlines the need to develop easily
applicable instruments for the assessment of DSM-5 AMPD personality functioning across
various mental disorders. In Study II, the German version of the SIFS self-report questionnaire could be such an easy-to-use instrument; nevertheless, our results indicate that it warrants
modifications for the use in research. However, a 22-item adapted version can be used as a
self-report questionnaire in clinical practice. Its psychometric properties in assessing the
general personality disorder (g-PD) factor are sufficient, but it shows insufficient structural
validity for the specific factors. Study III showed that among the variety of interview-rated
dimensions four PDS dimensions – defense mechanisms, desire and capacity for closeness,
sense of self with boundaries to others, and understanding and appreciation of experiences and
motivations of others – efficiently approximate the latent, method-adjusted g-PDS with 95.0%
explained variance. When combining two of these four dimensions, between 81.8% and 91.3%
of the latent g-PDS variance can be explained. Of note, measures of defense mechanisms are
lacking in the conceptualizations of the ICD-11 and DSM-5 AMPD. Regarding self-report
dimensions, we recommend assessing at least the identity and intimacy subdomains of
personality functioning.
Taken together, our studies establish that the assessment of personality functioning has
an important transdiagnostic value to somatization pathologies and their treatment. To facilitate
the diagnostic process, the SIFS can be used for a global impression of the level of personality
functioning, but should be used with caution in research. Finally, in time-limited practice, a
special emphasis should be placed on self-report and interview-assessed subdomains of identity
and intimacy to approximate the g-PDS. Furthermore, our results highlight the relevance of old
psychodynamic concepts, such as defense mechanisms, in contemporary transdiagnostic
personality pathology research.