Short-term versus long-term mentalization-based therapy for outpatients with subthreshold or diagnosed borderline personality disorder: a protocol for a randomized clinical trial

BACKGROUND: Psychotherapy for borderline personality disorder is often lengthy and resource-intensive. However, the current length of outpatient treatments is arbitrary and based on trials that never tested if the treatment intensity could be reduced. As a result, there is insufficient evidence to inform the decision between short-term and long-term psychotherapy for borderline personality disorder. Mentalization-based therapy is one treatment option for borderline personality disorder and consists traditionally of an 18-month treatment program. METHODS/DESIGN: This trial is an investigator-initiated single-center randomized clinical superiority trial of short-term (20 weeks) compared to long-term (14 months) mentalization-based therapy for outpatients with subthreshold or diagnosed borderline personality disorder. Participants will be recruited from the Outpatient Clinic for Personality Disorders at Stolpegaard Psychotherapy Centre, Mental Health Services, Capital Region of Denmark. Participants will be included if they meet a minimum of four DSM-V criteria for borderline personality disorder. Participants will be assessed before randomization, and at 8, 16, and 24 months after randomization. The primary outcome is severity of borderline symptomatology assessed with the Zanarini Rating Scale for borderline personality disorder. Secondary outcomes include self-harm incidents, functional impairment (Work and Social Adjustment Scale, Global Assessment of Functioning) and quality of life (Short-Form Health Survey 36). Severity of psychiatric symptoms (Symptom Checklist 90-R) will be included as an exploratory outcome. Measures of personality functioning, attachment, borderline symptoms, group alliance, and mentalization skills will be included to explore potential predictors and mechanisms of change. DISCUSSION: This trial will provide evidence of the beneficial and harmful effects of short-term compared to long-term mentalization-based therapy for outpatients with subthreshold or diagnosed borderline personality disorder. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03677037. Registered on September 19, 2018. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13063-019-3306-7) contains supplementary material, which is available to authorized users.