Comparison of 8-vs-12 weeks, adapted dialectical behavioral therapy (DBT) for borderline personality disorder in routine psychiatric inpatient treatment—A naturalistic study

Abstract Dialectical behavior therapy (DBT) is widely acknowledged as an effective treatment for individuals with borderline personality disorder (BPD). However, the optimal treatment duration within DBT remains a topic of investigation. This retrospective, naturalistic non-randomized study aimed to compare the efficacy of 8 week and 12 week DBT interventions with equivalent content, focusing on the change of BPD-specific symptomatology as the primary outcome and depressive symptoms as the secondary outcome. Overall, 175 patients who participated in DBT and received either 8 week or 12 week intervention were included in the analysis. Routine inpatient treatment was adapted from standard DBT with the modules: skill training, interpersonal skills, dealing with feelings, and mindfulness. Measurements were taken at baseline, mid-point, and endpoint. The borderline symptom list-23 (BSL-23) was used for the assessment of borderline-specific symptoms, while the Beck depression inventory-II (BDI-II) was used for the assessment of depressive symptoms. Statistical analysis was conducted using linear mixed models. Effect sizes were calculated for both measures. The results of the analysis indicated an improvement in both groups over time. Effect sizes were d = 1.29 for BSL-23 and d = 1.79 for BDI-II in the 8 week group, and d = 1.16 for BSL-23 and d = 1.58 for BDI-II in the 12 week group. However, there were no differences in the change of BPD-specific symptoms or the severity of depressive symptoms between the 8 week and 12 week treatment duration groups. Based on these findings, shorter treatment durations, like 8 weeks, could be a viable alternative, offering comparable therapeutic benefits, potential cost reduction, and improved accessibility. However, further research is needed to explore factors influencing treatment outcomes and evaluate the long-term effects of different treatment durations in DBT for BPD. Trial registration: drks.de (DRKS00030939) registered 19/12/2022.