Prepared by Michael B. First, M.D., DSM Consultant to the American Psychiatric Institute for Research and Education (APIRE), a subsidiary of the American Psychiatric Association
The first diagnosis-related research planning conference in the “Future of Psychiatric Diagnosis: Refining the Research Agenda” series, focusing on the diagnosis and classification of Personality Disorders in future diagnostic classifications (e.g., DSM-5 and ICD-11), was held on December 1-3, 2004, at the American Psychiatric Association headquarters in Arlington, VA. It was co-chaired by Thomas A. Widiger, Ph.D, from the University of Kentucky, in Lexington Kentucky, and by Erik Simonsen, M.D, of the Institute of Personality Theory and Psychopathology, Psychiatric Hospital, Fjorden, Denmark and included 23 invited participants from both the United States and internationally, who presented papers and/or served as discussants.
Both the DSM-IV and the ICD-10 use a categorical model for psychiatric diagnoses, i.e., a patient either has or does not have Schizophrenia, Bipolar Disorder, etc.). Categorical models of classification are used not only in making diagnoses of mental disorders but also in the diagnosis of medical conditions (e.g., a patient either has or does not have pulmonary tuberculosis), the classification of living organisms into families, genuses, and species, and virtually any other activity that involves classifying objects or concepts into types. Although categorical classifications work well in terms of modeling how clinicians think about disorders and diseases, they have many properties that deviate from the actual presentations of psychiatric symptoms. For example, categorical systems assume that there are clear boundaries delineating one condition from another and that there are specific boundaries between disorder and normality, as exemplified by the use of symptom thresholds for the determination of the presence or absence of disorder (e.g., 5 or more out of a list of 9 symptoms indicates the presence of a Major Depressive Episode whereas 4 or less indicate its absence). In fact, most psychiatric symptoms, like those characteristic of depression, occur on a continuum without any clear demarcations between disorder and normality. A classification that describes disorders in terms of points on a number of diagnostic continua is referred to as a “dimensional approach.”
Although the issue of how best to model psychiatric disorders (i.e., categorical, dimensional, or some combination of the two) applies to all of the disorders in DSM-IV and ICD-10, the problematic nature of the categorical approach is most evident in the diagnostic classification of personality disorders. As noted in the “Research Agenda for DSM-V”, there is widespread dissatisfaction among both clinicians and researchers with the current categorical system for personality disorders, which consists of determining whether an individual’s personality manifestations meet the diagnostic criteria for one or more specific DSM-IV personality disorders, such as borderline personality disorder, obsessive-compulsive personality disorder, and paranoid personality disorder. Problems with the current system include: 1) severely ill inpatients often meet criteria for three, four, five, or even more DSM-IV personality disorders, 2) outpatients typically do not meet the criteria for any of the specific categories, requiring instead use of the non-specific diagnosis Personality Disorder Not Otherwise Specified (PDNOS); 3) patients with the same diagnosis vary substantially with respect to which diagnostic criteria were used to make the diagnosis so that two patients with the same diagnosis can look very different; 4) the diagnostic thresholds separating normal from disordered are unstable so that the disorder can appear to come and go over time; and 5) the absence of a developing scientific base for a number of the diagnostic categories (e.g., histrionic, paranoid, schizoid, and obsessive-compulsive disorders).
Dimensional models of personality functioning and disorder have been studied for a number of years. In fact, during the DSM-IV deliberations, the adoption of a dimensional model for personality disorders was considered but ultimately rejected because of the number of competing and incompatible models that had been proposed by the research community, lack of empirical data regarding their validity, and questions about whether a dimensional system would be clinically useful.
The goal of this conference, therefore, was to stimulate research toward the development of a dimensional model of personality disorder that would have a strong empirical foundation with respect to behavioral genetics, neurobiological mechanisms, childhood antecedents, cross-cultural application, continuity with the rest of the diagnostic manual, coverage of clinical relevant maladaptive personality functioning, diagnostic thresholds, and treatment implications.
Proceedings of the Conference
The conference began with a presentation by Erik Simonsen, M.D. outlining the limitations of the categorical model for personality disorders (as described above) and was followed by a presentation by Thomas Widiger Ph.D. that presented the history of dimensional model of personality (including the three-factor model of Eysenck, the five-factor model of Zuckerman, the twenty-four traits and four dimensions of Tyrer, the three polarity model of Millon, the seven factor model of Cloninger, the three-factor model of Tellegen, Watson, and Clark, the five-factor model of Costa and McCrae, and the interpersonal circumplex model). Widiger then continued by calling for an integration of the various alternative dimensional models, pointing out most of the models share common higher-order domains that could allow for their integration into a unified four or five factor hierarchical model. Widiger indicated further how the existing DSM-IV personality disorder criteria could be integrated within this common hierarchical model. Lee Anna Clark, Ph.D. (Iowa City, Iowa), John Oldham, M.D (Charleston, S.C.)., and Professor Charles Pull (Luxembourg) served as discussants for these two initial presentations.
The next presentation was given by W. John Livesley (Vancouver, Canada) on the “Behavioral and Molecular Genetic Contributions to a Dimensional Classification of Personality Disorder.” Livesley noted that although it may make sense for future classifications (i.e., DSM-VI and beyond) to incorporate a provision for encoding genotypes that are associated with the increased likelihood of personality disorder, there is currently only very limited data supporting a relationship between genetic polymorphisms and personality traits, and the effects are small and relatively non-specific. Livesley then presented behavioral genetic research that seeks to explicate the genetic and environment structure underlying phenotypic variation. He concluded that it is possible to construct an etiologically-informed dimensional classification and that genetic methods can help in integrating the different dimensional schemes that have been proposed. Peter McGuffin, M.D., PhD (London, UK) and Benjamin Greenberg, M.D., Ph.D (Providence, Rhode Island) served as discussants.
Joel Paris M.D., (Montreal, Canada) next presented on the neurobiological dimensional models of personality, specifically reviewing the models of Cloninger, Depue, and Siever. He concluded that associations between dimensional trait measures and specific neurobiological measures remain ambiguous with the exception being a robust link between serotonin and impulsive aggression or harm avoidance. He postulated that the reason for this is that our understanding of the neuroscience of emotions and behaviors is currently at too early a stage and called for future research to help further elucidate the relationship between neurobiology and emotions. Robert Cloninger MD (St. Louis, MO) and Professor Peter Tyrer (London, UK) were the discussants for this presentation.
Ivan Mervielde Ph.D. (Gent, Belgium) then presented on “Childhood Antecedents and Developmental Psychopathology.” He first reviewed the evidence for a dimensional presentation of childhood temperament and personality. He proposed that four broadband dimensions capture individual differences in personality in children and adolescents: extraversion, emotional stability, agreeableness, and conscientiousness; that two dimensions describe childhood psychopathology: externalizing and internalizing; and that these personality and psychopathology dimensions can be related to each other using a hierarchical model. Rebecca Shiner, Ph.D. (Hamilton, NY) served as discussant.
Dr. Juri Allik (Tartu, Estonia) presented on “Personality Dimensions Across Cultures.” He reported on studies examining personality dimensions measured in a wide variety of cultures and languages. Although such data remains limited, the data support the hypothesis that covariation among personality traits is universal and extends across languages and cultures, including both Western and non-Western. Mean trait scores did vary across cultures, although cross-cultural differences were only a third of the magnitude of individual differences within a culture. Allik noted that this small magnitude cross-cultural difference suggests that it is possible to achieve a reasonable scalar equivalence irrespective of language and culture. Michael Ashton, Ph.D (St. Catherine’s, Canada), Juan Lopez-Ibor, MD (Madrid, Spain), and Yueqin Huang MD, PhD (Beijing, China) served as discussants.
A presentation addressing the continuity of Axis I and Axis II Disorders was given by Robert Krueger, PhD (Minneapolis, MN). Krueger began by reviewing the putative differences between Axis I and Axis II disorders, concluding that they are more similar than distinct. He then proposed that the connection between Axis I and Axis II disorders may be provided by a focus on how they are both connected to the underlying structure of personality. He proposes a hierarchical structure of mental disorders that integrates both the psychopathology represented by Axis I disorders with personality traits. It consists of two higher level factors (externalizing and internalizing), five mid-level dimensions (corresponding to those in the five factor model), and lower order facets. Tracie Shea, Ph.D (Providence, RI), David Watson, PhD (Iowa City, Iowa), and Deborah Hasin PhD (New York, NY) were the discussants.
Timothy Trull, PhD (Columbia, MO) presented a paper focusing on what he described were the two major challenges that must be addressed by dimensional models if they are to be considered viable alternatives to the categorical system: coverage (i.e., whether the system adequately characterizes conditions that are encountered in clinical practice) and cutoffs (i.e., how to make the judgment that personality pathology is sufficiently severe to warrant clinical attention). He first compared the coverage of several of the dimensional systems by noting their relationship to the DSM-IV personality disorder categories as well as their content validity and noted that the four higher order dimensions that these systems have in common support the possibility of integration of the dimensional systems. He then reviewed general issues for determining whether a personality disorder is present, (including statistical deviance and consequent dysfunction and impairment) and then evaluated several proposals for using dimensional models to diagnose personality disorder, recommending that future research focus on how best to define clinically significant dysfunction. Drew Westen, PhD (Atlanta, GA), Paul Costa, PhD (Baltimore, MD), and Carl Bell, M.D. (Chicago, IL) were the discussants.
The final presentation, by Roel Verheul, PhD (Halsteren, the Netherlands) covered the “Clinical Utility of Dimensional Models of Personality Pathology.” He argued that a dimensional diagnostic system will substantially improve clinical utility, especially with respect to coverage, reliability, subtlety (i.e., level of detail and richness) and clinical decision making. Verheul notes, however, that whatever dimensional model is chosen in the future, it cannot entirely replace a categorical system, which will continued to be needed for legal, medical, and administrative purposes. Erik Simonsen (Denmark) and Theresa Wilberg (Oslo, Norway) acted as discussants.
The conference concluded with a discussion of the various research strategies that will enrich the empirical base for making future decisions about the classification of personality disorders.
The presentations were published in a special edition of the Journal of Personality Disorders and both the main presentations and discussants’ responses were published in a future monograph by American Psychiatric Publishing, Inc., which can be purchased here.