Effects of Short‐Term Versus Long‐Term Mentalization‐Based Therapy on Psychiatric Symptoms in Outpatients With Borderline Personality Disorder: Exploratory Results From a Randomized Clinical Trial

We conducted a randomized clinical trial assessing the beneficial and harmful effects of short-term versus long-term mentalization-based therapy (MBT) for outpatients with borderline personality disorder (BPD) and found no evidence of a difference on BPD symptom severity, functional impairment, quality of life, global functioning, and severe self-harm. In this paper, we assessed the effects of short-term versus long-term MBT on the exploratory outcome, psychiatric symptoms, assessed with the Symptom Checklist-90-Revised (SCL-90-R). Participants included the full intention-to-treat sample of the original trial of N = 166 randomized outpatients with subthreshold or a diagnosis of BPD (short-term MBT n = 84, long-term MBT n = 82), who were randomly assigned to short-term MBT (5 months) or long-term MBT (14 months). Psychiatric symptoms were assessed with the SCL-90-R at baseline, 8, 16, and 24 months after randomization. The 16-month time point was predefined as our time point of primary interest. Regression analyses showed no evidence of a difference when assessing general symptom severity (MD -0.02, 95% CI -0.24-0.20; p = 0.841) or any of the subscales, including anxiety, depression, hostility, interpersonal sensitivity, obsession/compulsion, paranoid ideation, phobic anxiety, psychoticism, and somatization. At the exploratory 24-month follow-up time point, similar results were obtained. In conclusion, short-term MBT neither weakened nor improved patients' psychiatric symptoms compared with long-term MBT for outpatients with BPD. Trial Registration: ClinicalTrials.gov: NCT03677037.