Changes and dilemmas in the diagnosis of personality disorders: How do both clinical and forensic psychologists and psychiatrists decide which model to choose?

Author Identifier

Lisa Dawson: https://orcid.org/0000-0001-8968-0337

Date of Award

2025

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Doctor of Psychology (Clinical and Forensic)

School

School of Arts and Humanities

First Supervisor

Deirdre Drake

Second Supervisor

Greg Dear

Abstract

This study was developed following the first attempt by the Diagnostic and Statistical Manual of Mental Disorders (DSM) since the DSM-III to change the way personality pathology is described, understood, and diagnosed. This change has led to research and debates about whether a personality model for diagnosis should be categorical, dimensional, or a combination of the two (a hybrid model). While the literature has focused on comparing models for personality disorder (PD) diagnosis across clinical settings and across measures of validity, reliability, and clinical utility, my research addresses how psychologists and psychiatrists decide which model to use for both therapeutic purposes and forensic purposes. I used two studies to explore this area of inquiry. The first was a qualitative study to explore how psychologists and psychiatrists decided whether to use the Alternative Model for Personality Disorders proposed in the DSM-5. From this study, 16 statements that represent decision factors were developed for further quantification in a survey, which was the second study. I identified the factors that most influenced psychologists’ and psychiatrists’ decisions regarding which currently available formal diagnostic model (within DSM and International Classification of Diseases (ICD)) to use for PD diagnosis. I also explored current preference for the categorical, hybrid, or dimensional model of PD. Replicating previous research, I found that psychologists and psychiatrists prefer dimensional models of PD over categorical models. The most influential decision factors are the usefulness of the diagnostic model for communicating personality information to peers and in assessment reports, and the diagnostic model’s usefulness for describing the personality difficulty of the person being assessed or treated. Knowledge about the model, previous training, and the amount of training in the PD model represent practical issues that practitioners consider when making decisions on which PD model to use. The results identify important influencing factors that can create bias in the results when comparing models for diagnosis, such as previous training, which was more influential than a practitioner’s theoretical orientation and is an important consideration for research in this area. The inclusion of a clinical utility measure that captures communication in assessment reports is also recommended, especially for research exploring models for forensic purposes. Forensic practitioners place greater weight on the acceptance of a PD model by experts in the field than they do when choosing a model to use in their therapeutic work. My results, if replicated, provide a better set of criteria for exploring views about assessment measures and diagnostic models for PDs, including which clinical utility factors to focus on.

Access Note

Access to this thesis is embargoed until 4th May 2027

DOI

10.25958/jwxv-hx25

Access to this thesis is restricted. Please see the Access Note below for access details.

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