Revising and assessing axis II, Part II: toward an empirically based and clinically useful classification of personality disorders.
OBJECTIVE: The DSM-IV classification of personality disorders has not proven satisfying to either researchers or clinicians. Incremental changes to categories and criteria using structured interviews may no longer be useful in attempting to refine axis II. An alternative approach that quantifies clinical observation may prove useful in developing a clinically rich, useful, empirically grounded classification of personality pathology. METHOD: A total of 496 experienced psychiatrists and psychologists used the Shedler-Westen Assessment Procedure-200 (SWAP-200) to describe current patients diagnosed with axis II personality disorders. The SWAP-200 is an assessment tool that allows clinicians to provide detailed, clinically rich descriptions of patients in a systematic and quantifiable form. A statistical technique, Q-analysis, was used to identify naturally occurring groupings of patients with personality disorders, based on shared psychological features. The resulting groupings represent an empirically derived personality disorder taxonomy. RESULTS: The analysis found 11 naturally occurring diagnostic categories, some of which resembled current axis II categories and some of which did not. The findings suggest that axis II falls short in its attempt to "carve nature at the joints": In some cases it puts patients who are psychologically dissimilar in the same diagnostic category, and in others it makes diagnostic distinctions where none likely exist. It also fails to recognize a large category of patients best characterized as having a dysphoric personality constellation. The empirically derived classification system appears to be more faithful to the clinical data and to avoid many problems inherent in the current axis II taxonomy. CONCLUSIONS: The approach presented here may be helpful in refining the existing taxonomy of personality disorders and moving toward a system of classification that lies on a firmer clinical and empirical foundation. In addition, it can help to bridge the gap that often exists between research and clinical approaches to personality pathology.