Biology of Personality Disorders

Biology of Personality Disorders

Annual Review of Psychiatry series

Silk KR. Washington: American Psychiatric Press; 1998. 156 pp

ISBN 0-8804-883-52

This book, part of the Annual Review of Psychiatry series, is a multi-authored text comprising 5 chapters by recognized authorities in the field. The topic is of interest because of the increased activity in the area of personality disorders over the past decade and a half with respect to typology, research and new treatment approaches. This book focuses on research into the biological aspects of personality disorders over the last 10 years or so. As Silk points out in the Foreword, earlier studies of biological correlates of personality disorders did not lead to clear conclusions because of lack of appropriate separation between personality disorders and Axis I disorders. The “second-generation” studies have focused on the core negative traits of personality disorders (e.g., impulsivity, aggression, cognitive disturbances and affective lability, which cut across most personality disorders) and sought to understand their biological underpinnings.

The first 2 chapters of the book review and discuss the biological research in the field, including research strategies employed, the results of some of the most important studies and the implications for further development.

The first chapter, by Coccaro, reviews studies of neurotransmitters that are significant for personality functioning. The most important of these are serotonin and the cate-cholamines, including dopamine and norepinephrine. The studies are reviewed under categorical headings including cerebrospinal fluid (CSF) metabolite studies, pharmacological challenge studies, platelet receptors and DNA in polymorphism studies, etc. The studies consistently find an inverse relation between CSF 5-HIAA levels and impulsive-aggressive behaviour.

There is a smaller body of research into the role of acetylcholine and vasopressin, which shows that acetycholine does contribute to affective lability.

The second chapter, entitled “New Biological Research Strategies for Personality Disorders” by Siever and colleagues, complements the first. It reviews studies using a variety of recently developed strategies to study core traits of impulsivity, affective instability and cognitive dysfunction. The strategies vary from neuroendo-crine and cognitive studies that look at the antecedents of neuroendocrine and cognitive abnormalities found in personality disorders, to the use of imaging (positron-emission tomography, single-photon emission computed tomography, magnetic resonance imaging [MRI] and functional MRI) to study neuroanatomical correlates of personality dysfunctional traits such as impulsivity and aggression. There are fewer studies using candidate gene strategies. The author comments on the implications of the findings to date from these areas of investigation.

A particularly creative strategy was the linking of the study of trauma to personality disorders. Trauma has its biological impact on the hypothalamic-pituitary-adrenal (HPA) axis, but trauma is also a major etiologic factor in many personality disorders, including borderline personality disorder (BPD). Studies of the HPA axis changes, such as dexamethasone suppression test (DST) in patients with post-traumatic stress disorder, have been extended to personality disorders as BPD, with the DST pattern more closely resembling that in PTSD than that in mood disorders.

The third chapter focuses on Cloninger’s proposed 7-f actor model of personality, comprising temperamental factors such as harm avoidance, novelty seeking, reward dependence and persistence, and 3 character elements: self-directedness, cooperativeness and self-transcendence. Cloninger makes the case for the neurobiological basis of learning abilities that underlie temperamental traits by summarizing studies of the psychobiological correlates of these traits. He then puts forward a psychobiological learning model based on his review of the neuropharmacological, neuroanatomical and biochemical studies, and on studies of the phylogeny of learning abilities. He concludes by making a strong argument in support of the 7-factor model as a basis for understanding the various dimensions of personality disorder and even the diagnostic clusters. Although much of the material is quite technical, the use of tables and other visual aids is helpful in summarizing and reinforcing the material presented in the text.

The last 2 chapters are more application-oriented. The fourth chapter, by Links, is interesting because of the proposal of an outcome-based approach to the pharmacotherapy of personality disorders. Outcome indicators would be reduction in certain characteristic behaviour patterns, such as repetitive self-injury, that have been shown to have a biological basis. Other outcome indicators include quality of life. The author notes the shortcomings of the current conceptual models of personality disorder as a basis for developing a treatment rationale. The outcome-based model proposes specifically desirable functional outcomes of treatment and more systematic approaches to assessment of the efficacy of medication. This proposal is very much in keeping with the current evidence-based approach to medical practice.

In the final chapter, Paris assesses the significance of research for a biopsychosocial model of personality disorders. The author points out inconsistencies between theoretical assumptions underlying some research strategies and real-world observations, as well as the many confounding factors that complicate the search for one-to-one correlations between biological variables and particular personality traits. Taking a dimensional view of personality disorders as the pathological amplification of normal traits, the author discusses the complicated interaction of biological and environmental factors in producing personality disorders via the diathesis-stress model. He proposes 3 potential research directions: new drugs targeting personality traits, gene therapy, and new forms of psychotherapy based on better understanding of temperament.

Since much of the research on impulsivity and aggressiveness reviewed is common to conduct disorder and attention deficit hyper-activity disorder as well as anxiety disorders in children, one would have expected a discussion of the relation of these conditions to personality disorders in adults. Despite this lack, I found this book to contain more than anticipated. The material in the first 3 chapters was detailed and informative, and the last 2 chapters helped to make it practically relevant. One is left with a feeling that personality disorders are now more real, and that there is hope for more targeted treatment in the future. I certainly recommend it.