The goal of this study was to evaluate whether symptoms are reduced and emotion regulation improves when patients with borderline personality disorder (BPD) receive a 5-week course of inpatient dialectical behavioral therapy (DBT) and if changes in emotion regulation are associated with changes in symptoms. Methods: Forty-four patients with BPD receiving a 5-week course of DBT in a German psychiatry clinic participated. The short version of the "Borderline Symptom List" (BSL-23) was the patient-reported outcome. To measure emotion regulation, the "Self-Report Measure for the Assessment of Emotion Regulation Skills" (SEK-27) was administered. Wilcoxon tests were performed to evaluate whether pre-post changes in the BSL-23 and SEK-27 reached statistical significance. Effect sizes (d) were calculated and correlations between the prepost differences for both measures were computed to test associations between changes in emotion regulation and changes in symptoms. Completer (n = 33) and intention-to-treat (n = 43) analyses were performed. Results: Symptoms (BSL-23) were reduced and emotion regulation (SEK-27) improved during the 5-week inpatient DBT treatment (completer and intention-to-treat analysis: P < 0.001). Effect sizes reached d = 0.47 for the BSL-23 and d = 0.84 for the SEK-27 in the completer analysis, and d = 0.38 for the BSL-23 and d = 0.68 for the SEK-27 in the intention-to-treat analysis. Improvements in emotion regulation (SEK-27) were correlated with reductions in symptoms (BSL-23) in both the completer (r = 0.54; P = 0.001) and the intention-to-treat (r = 0.59; P < 0.001) analyses. Conclusions: These findings indicate that a 5-week course of inpatient DBT can effectively reduce symptoms in patients with BPD and that the more patients' emotion regulation improves, the more the patients benefit from the therapy.

Associations between suicidal ideation and skill use were investigated during in-patient dialectical behavior therapy (DBT) for borderline personality disorder (BPD). Participants were N = 44 patients with BPD undergoing a 5-week in-patient DBT program in a psychiatric clinic. They filled in a diary card each treatment day resulting in 1,334 skill use ratings and 1,364 suicidal ideation ratings. Treatment days were categorized as days with successful skill use (using skills and perceiving them as effective), days with no skill use, days with unsuccessful skill use (using skills but perceiving them as ineffective). Multilevel models were performed to account for the nested data structure. The results showed that suicidal ideation improved more for patients who applied skills successfully more often during treatment (p < 0.05). Moreover, suicidal ideation was lower on treatment days with successful skill use compared to treatment days with no skill use and compared to treatment days with unsuccessful skill use (p < 0.05). When treatment days with no skill use were compared to treatment days with unsuccessful skill use, suicidal ideation was higher on treatment days with unsuccessful skill use (p < 0.05). To conclude, using skills successfully on as many treatment days as possible is associated with lower suicidal ideation.