Abstract
BACKGROUND: Dialectical behavioral therapy (DBT) and repetitive transcranial magnetic stimulation (rTMS) are both effective in treating borderline personality disorder (BPD). Impulsivity and impaired decision-making are prominent features of BPD, and therapeutic interventions targeting these symptoms could lead to significant improvements. OBJECTIVE/HYPOTHESIS: We hypothesized that intermittent theta burst stimulation (iTBS), a modified rTMS protocol that targets the left dorsolateral prefrontal cortex, would enhance the therapeutic effects of DBT, leading to greater improvements in impulsivity and decision-making compared with sham stimulation. METHODS: We performed a single-blind, randomized, sham-controlled pilot study to evaluate the efficacy of iTBS as an add-on to an 8-week DBT program for BPD in a routine inpatient setting. A total of 53 BPD patients were randomly assigned to receive either iTBS (n = 25) or sham stimulation (n = 28) during weeks 4 to 8 of DBT, and 36 patients met the inclusion criteria for the present analysis (≥ 16 of 20 iTBS/sham sessions and assessment of delay discounting). The study endpoints were the Barratt Impulsiveness Scale-15 for impulsivity and the Monetary Choice Questionnaire for decision-making/delay discounting. RESULTS: A mixed model repeated measures analysis with a 2 × 2 factorial between-subjects design showed a significant overall improvement over time in impulsivity but not in decision-making/delay discounting. No significant differences were found between iTBS and sham, although post hoc tests revealed significant changes in impulsivity in the iTBS group (mean(diff) = -4.7, p = .001, Cohen's d = 0.68) but not in the sham group (mean(diff) = -2.1, p = .077, d = 0.31). CONCLUSIONS: iTBS may offer long-term benefits as an add-on treatment to DBT for impulsivity in BPD, suggesting the need for further investigation in larger-scale studies. TRIAL REGISTRATION: Registered at drks.de (no. DRKS00020413) on January 13, 2020.