Today, the field of personality disorder is impossibly disordered. In place of a unitary theory, we have tens of competing theories. For the most part, these theories are not free-floating but are anchored by evidence. However, this evidence is itself incoherent and contradictory. Every aspect of nosology is subject to contention : the boundary between health and illness, boundaries between personality diagnoses, and boundaries between personality disorder and "Axis One" diagnoses. Depending on one's perspective, this disarray is either distressing or hopeful-the sign of a richness of conceptualization that is appropriate to the current state of knowledge.
Theory is the appropriate battleground because there is as yet no consensus, and no grounds for consensus, about the wider context of which personality disorder will be a part. That is to say, there is no predominant theory of personality and little clarity about the chronic effects or enduring causes of acute mental illness. The very terms that are used to build theory temperament and character, state and trait, axis one and axis two, nature and nurture have become the object of dispute, and a new confusing vocabulary has come into play : function, dimension, pleiotropy, phenocopy, and a whole list of specific concerns from affectivity to sociotropy.
Perhaps the most interesting set of questions, joined even in the absence or a satisfying definition of the personality disorders, concerns the relationship of marked personality traits to mental illness. How does impulsivity relate to conduct disorder, anxiety to anxiety disorder, depression to melancholy, and all of these traits to the ever-frustrating, ever-promising borderline personality disorder ? Here, the theory-building has been especially vigorous. Two opposing suspicions have predominated : that subclinical mental illness leads to personality disorder ; and that extremes of temperament are at the root of mental illness. Perhaps much of what has been understood as personality disorder should be redefined and treated as mood disorder unless much of what has been understood as mood disorder should be redefined and treated as an intermittent consequence of temperament.
Contradictory evidence bearing on this dispute has made alternative approaches seem attractive, especially an appeal to dimensions or functions, such as affectivity, aggression, and impulsivity, that might underlie both personality and illness. This approach was most attractive when first elaborated when it seemed that two or three dimensions might suffice to explain the more common personality variants and mental disorders. Common clinical responses of personality and illness to a limited variety of medications strengthened the case for a dimensional approach. But with time, the number of dimensions required to explain the data has multiplied, new theories have arisen to explain the medication effects, and the question of causality has gotten no simpler. What is the basis of the dimensions ? Early attemps at applying data to theories of causation seem only to indicate that all the simple theories must be wrong.
In response, genetic model-making has demonstrated its own complexity. Perhaps genes are expressed as temperamental phenotypes that constitute a liability to mental illness. But what if the same gene, the one that shapes temperament, has direct and independent effects on illness ? And what if a second gene differentially modifies the two propensities, for personality type and emotional fragility ? When we talk on the level of neurotransmitters, the problems do not disappear. Perhaps variations in the same neurotransmitter have quite different effects when expressed in different regions of the brain. In a sense, the field of personality disorder is awaiting clarification from genetics. Until we know where genes act, we will doubt whether we have got classification and causation right-and well will doubt our theories about the effect of social environment.
What has become clear in the meanwhile is how difficult psychiatry is as a clinical science. Consider the case of chronic depression. Is it a state or a trait ? Personality or illness ? And what are its characteristic manifestations ? In Germany, depressives are so rigid, judgmental, and self-critical that it appears scrupulosity may be the fundamental trait underlying melancholy. In the United States, depression seems strongly linked to sensitivity and impulsivity. Apparently, there are two sorts of chronic depressives-to use shorthand, the obsessives and the hysterics.
To a degree, this confusion and sense of promise accurately reflect the empathic experience of clinical psychiatry. Faced with the individual patient, the clinician is aware of the limitations of personality diagnosis. In the details of personality, one depressive does not resemble another. And yet these varied and contradictory accounts of chronic depression do seem useful. It does make sense to consider scrupulosity and sensitivity ; it does help to ask in the clinical moment which is primary, the mood disorders or the temperament, and which the medication or psychotherapy is targeting. It helps to ask whether or not the phenotype the personality is leading to disappointments that lead to mood disorder, or whether the mood disorder is creating what might be called a false or distorted personality. What is biological bedrock and what is environmentally malleable ? The issue of phenocopies is clinically intriguing when is a depression not a depression ; when is depressive personality something else entirely ? These issues have significance even for the pure pharmacologist, since research hints that temperament may predict differential medication responsiveness. As is so often the case in psychiatry, imperfect scientific concepts serve as provocative metaphors in the consulting room and this is the case whether or not the chosen intervention is psychotherapy. If nothing else, the frustrations of research have led to provocative myth-making for clinical practice.
