The effectiveness of cognitive analytic therapy for borderline personality disorder: Utilizing a withdrawal...

A primary methodological weakness of the single-case experimental design (SCED) outcome studies conducted of the treatment of personality disorder with cognitive analytic therapy (CAT) is that they have failed to employ a withdrawal phase or cross-over design and so are deemed quasi-experimental. This study sought to implement a withdrawal design, in order to improve the internal validity of the study to make it a true SCED, and also in order to enable the patient to explore abandonment dynamics.

The study employed an A¹ /B¹ /A² /B² with extended follow-up SCED with a female patient treated with CAT meeting diagnostic criteria for borderline personality disorder (BPD). Following the 6-week baseline period 'A¹ ', treatment occurred in two phases (21 sessions 'B¹ ' and 24 sessions 'B² ') sandwiching a 12-week treatment withdrawal phase ('A² ') and a 24-week structured follow-up phase. Seven idiographic daily measures were collected that created a N = 698 day timeline. Nomothetic outcome measures were collected at baseline and at the end of each phase of the study, and the Session Impact Scale was completed after each treatment session.

There was a significant increase in the task focus of treatment sessions. Ideographically, CAT was an effective treatment for improving the participant's self-to-self relationship, as their self-hate reduced and their sense-of-self increased. There was a broad pattern of deterioration during the second treatment phase (B² ) and follow-up phase across the ideographic measures, and CAT was ineffective for BPD ideographic emotional or self-to-other measures. Reliable change occurred on the primary BPD nomothetic outcome measure from baseline to end of first treatment phase.

The study suggests that the CAT intervention was partially successful and that it is possible to integrate good research practice with clinical innovation. The methodological strengths and limitations of the design and the clinical implications of the results are discussed.

Cognitive analytic therapy was partially effective in the treatment of BPD in a case that had been unresponsive to other psychological interventions. Therapists need to complete lengthy and structured follow-up to capture any emerging relapse. Therapists need to discuss the patient's thoughts and feelings about termination regularly in a relationally informed manner.