Impact of clinical severity on treatment response in a randomized controlled trial comparing day hospital and intensive outpatient mentalization-based treatment for borderline personality disorder

This study examined the impact of clinical severity on treatment outcome in two programs that differ markedly in treatment intensity: day hospital mentalization-based treatment (MBT-DH) and intensive outpatient mentalization-based treatment (MBT-IOP) for borderline personality disorder (BPD). A multicenter randomized controlled trial was conducted. Participants include the full intention-to-treat sample of the original trial of N = 114 randomized BPD patients (MBT-DH n = 70, MBT-IOP n = 44), who were assessed at baseline and subsequently every 6 up to 36 months after start of treatment. Outcomes were general symptom severity, borderline features, and interpersonal functioning. Clinical severity was examined in terms of severity of BPD, general symptom severity, comorbid symptom disorders, comorbid personality disorders, and cluster C personality features. None of the severity measures was related to treatment outcome or differentially predicted treatment outcome in MBT-DH and MBT-IOP, with the exception of a single moderating effect of co morbid symptom disorders on outcome in terms of BPD features, indicating less improvement in MBT-DH for patients with more symptom disorders. Overall, patients with varying levels of clinical severity benefited equally from MBT-DH and MBT-IOP, indicating that clinical severity may not be a useful criterion to differentiate in treatment intensity.