Dimensional Diagnosis of Personality--Not Whether, but When and Which

I find myself in almost total agreement with Widiger's arguments against the categorical method of personality diagnosis, but I disagree with the conclusions he draws from them. Widiger is correct that categorical diagnosis establishes a procrustean bed based on an inherently futile attempt to type a continuum that is without clear boundaries. The categorical method results in lost information, reduced reliability, and a cumbersome and artificial co-morbidity. Someday (perhaps in time for the fifth edition of the Diagnostic and Statistical Manual ofMental Disorders [DSM-V]), we will almost certainly be applying a dimensional model of personality diagnosis. In my view, however, the time is not ripe, and it is not yet clear which dimensional system will be optimal. Moreover, there may be certain situations in which the categorical approach remains preferable, and we should not assume that a dimensional approach will ever completely supplement the categorical. I elaborate briefly on each of these points. The reader will note that Widiqer has also raised and has attempted to rebut these very same arguments. Widiger and I agree on these issues and differ only in the emphasis we place on them. Why do I believe that the time is not yet ripe? DSM-IV is a method of diagnosis intended primarily for use by clinicians. DSM-IVis meant to be a conservative document, and the DSM-IV Task Force has established a high threshold for making changes. All revisions must be backed by compelling empirical evidence that the change is warranted. This is intended to reduce the disruption created by a new diagnostic system that is following so recently upon DSM-III (American Psychiatric Association [APA], 1980) and DSM-III-R (APA, 1987). It is also a priority thatDSMIV be as compatible as possible with the International Classification of Diseases 10, which continues to use a categorical system of personality diagnosis. That dimensional methods of personality diagnosis are cumbersome and unfamiliar to clinicians is a much larger problem than Widiger suggests. Although the categorical method has all sorts of problems and limitations, especially in the research setting, it does have a long historical tradition precisely because it conforms to the way clinicians work. The categories may provide no more than prototypical descriptions, but this is the way that clinicians make all their diagnoses-including those covered by Axis I. It will require a monumental educational effort before a dimensional system will be accepted by clinicians. Moreover, we do not yet know which dimensional system to educate them in. There are many competing systems and instruments to tap them. These overlap a great deal. Although it may be possible eventually to develop a widely accepted line-up of dimensions and a method of evaluating them, this is not the case now. During the last 7 years, I have attended three conferences that had as a goal the effort to develop a consensus dimensional system. None of these efforts succeeded because none of the available systems is clearly superior to the others, and the creators of the various systems believe it is premature to combine forces. If it is premature to develop a consensus of dimensions and instruments for research purposes, it is certainly premature to suggest that any one system is ready for introduction in a diagnostic manual meant for general clinical use. Furthermore, there is the assessment question. The available dimensional systems are generally derived from self-report assessment instruments that may not be optimal as the only source of information for clinical diagnosis. We do not know how well and reliably dimensional distinctions will play in clinical practice. It will take many years before such information is available, and this is a prerequisite to inclusion in an official nomenclature. We should also be aware that categorical diagnosis may have a continued utility, albeit a limited one. There is an economy of communication and vividness of description in a categorical name that may be lost in a dimensional profile. Borderline personality disorder is a category with numerous problems-but it offers a research and treatment target that may deserve a separate name, not a series of numbers. The terms schizotypal, paranoid, compulsive, avoidant (and so forth) personality disorders all call forth useful images that would be lost in a profile. As Widiger points out, it is no accident that the Minnesota Multiphasic Personality Inventory is usually reduced to types when it is applied in clinical practice. Where do things stand then? Dimensional systems are definitely superior for many if not most research purposes and need to be developed further. It would be useful before very long to achieve a consensus on the dimensions of greatest interest and to develop a consensus method of assessing them. It is important to educate