Quasi-experimental N = 1 evaluation of the effectiveness of cognitive analytic therapy for dependent personality disorder

The evidence base for the treatment of dependent personality disorder (DPD) is sparse and there are few credible evaluations of the effectiveness of integrative psychotherapies. This study therefore employed an A/B with extended follow-up quasi-Experimental single case design with a female patient meeting diagnostic criteria for DPD, treated with cognitive analytic therapy (CAT). The patient was treated with the 24-session version of the model, with 6 months structured follow-up. Fidelity to the treatment model was found to be satisfactory. There was a significant effect of phase of study in the time series of the primary idiographic measure of reassurance-seeking. On the primary nomothetic measure (i.e., the Interpersonal Dependency Inventory), there was a reliable improvement to self-confidence on assessment-termination comparisons. Confidence in the reliability of the idiographic results is limited by evidence of improvements occurring during the baseline phase. The methodological limitations and clinical/theoretical implications are discussed for the use of integrative psychotherapies with patients with strong dependent traits.