Abstract
The formal adoption of the ICD-11 Personality Disorder (PD) diagnosis in January 2022 marked the advent of major shift in the conceptualisation of PDs. Historically, PDs have been discrete categorical constructs, with polythetic checklists of symptoms. The ICD-11 reconceptualises PDs through the lens of a personality impairment dimension and maladaptive personality traits. Dimensional PD operationalisation is purported to solve the multitude of issues with the categorical model. However, little scientific research to date has examined the reliability and validity of the ICD-11 PD diagnostic components. The current thesis includes four empirical studies which examine the reliability and validity of the ICD-11 PD components, i.e. personality impairment and maladaptive personality traits, as well as specific assessment modalities developed to assess the ICD-11 PD. The final study surveyed Aotearoa/New Zealand clinicians for their perspectives on the clinical utility of the ICD-11 PD. Overall, the results of the current thesis provide evidence for the reliability and construct validity of the ICD-11 PD components. Aotearoa/ New Zealand clinicians indicate support for the move toward dimensional PD assessment, although raise concerns for the application of the ICD-11 PD within Aotearoa/ New Zealand. The thesis concludes with recommendations for future research into treatment options for the ICD-11 PD.