Abstract

Introduction In the treatment of borderline personality disorder (BPD), there is empirical support for both dialectical behavior therapy (DBT) and schema therapy (ST); these treatments have never been compared directly. This study examines whether either of them is more effective than the other in treating patients with BPD. Methods In this randomized, parallel-group, rater-blind clinical trial, outpatients aged between 18 and 65 years with a primary diagnosis of BPD were recruited in a tertiary outpatient treatment center (Lübeck, Germany). Participants were randomized to DBT or ST with one individual and one group session per week over 1.5 years. The primary outcome was the BPD symptom severity assessed with the mean score of the Borderline Personality Disorder Severity Index at 1-year naturalistic follow-up. Results Between November 26, 2014, and December 14, 2018, we enrolled 164 patients (mean age = 33.7 [SD = 10.61] years). Of these, 81 (49.4%) were treated with ST and 83 (50.6%) with DBT, overall, 130 (79.3%) were female. Intention-to-treat analysis with generalized linear mixed models did not show a significant difference at 1-year naturalistic follow-up between DBT and ST for the BPDSI total score (mean difference 3.32 [95% CI: -0.58-7.22], p = 0.094, d = -24 [-0.69; 0.20]) with lower scores for DBT. Pre-to-follow-up effect sizes were large in both groups (DBT: d = 2.45 [1.88-3.02], ST: d = 1.78 [1.26-2.29]). Conclusion Patients in both treatment groups showed substantial improvements indicating that even severely affected patients with BPD and various comorbid disorders can be treated successfully with DBT and ST. An additional non-inferiority trial is needed to show if both treatments are equally effective. The trial was retrospectively registered on the German Clinical Trials Register, DRKS00011534 without protocol changes.