Background: Mindfulness skills training is a core component of dialectical behavior therapy (DBT) that has proven to be an effective stand-alone treatment for the general symptoms commonly present in patients with borderline personality disorder (BPD). The aim of the present study was to compare the effectiveness of mindfulness-based DBT skills training (DBT-M) to interpersonal effectiveness-based DBT skills training (DBT-IE) in reducing BPD symptoms. We also evaluated the specific mechanism of action of these therapies through two proposed mediators: decentering and emotion dysregulation.
Method: A total of 102 participants diagnosed with BPD were included in the study. Multivariate repeated-measures ANOVAs were performed followed by a multiple mediation analysis.
Results: The analyses showed that DBT-M was more effective than DBT-IE in reducing BPD symptoms, although both interventions were effective in reducing emotion dysregulation. We identified a serial mediation model in which DBT-M reduced BPD symptoms by increasing decentering ability, which in turn reduced emotion dysregulation. This mediation effect showed that changes in decentering preceded improvements in emotion dysregulation.
Conclusions: These findings underscore the key role of decentering as a primary mechanism of action in DBT-M, suggesting that this skill is a main component for BPD treatment.