Factors Affecting Treatment Outcome in a Naturalistic Study of Psychological Therapy for Personality Disorder

This three-part thesis focuses on psychological therapy for personality disorders (PDs) and factors that influence both treatment completion and outcome. Part one is a literature review investigating documented mechanisms of change in the cognitive behavioural therapy (CBT) and dialectical behavioural therapy (DBT) treatment for borderline personality disorder (BPD) in current research. Although much research has focussed on improving treatment outcomes for BPD, there is very little research investigating the proposed changes by which these outcomes might occur. Three distinct categories of mechanism of change were found to be consistent across the literature examined. These categories are discussed in detail along with implications for future research and clinical practice. Part two presents a longitudinal empirical study of factors which affect treatment completion and treatment outcome in the CBT or DBT treatment of PD. Data spanning a six year period was collected and analysed for 231 patients. Results showed that therapist expertise was the only variable examined associated with treatment completion: more experienced therapists retained their patients in treatment for longer than less experienced therapists. Therapeutic dose (number of sessions attended), therapist expertise and substance misuse all predicted changes in risk outcome (deliberate self-harm, suicide attempts) and in number of PD diagnoses following treatment. Only therapeutic dose predicted change in other clinical diagnoses following treatment. Implications and strength of these findings are discussed in relation to problems with incomplete data, statistical analyses and non-representative sampling issues. Part three is a critical appraisal of the entire research process reflecting upon its challenges and successes. This section also includes a commentary on the field of PD research in general, and considers issues pertinent to future research