Differential effectiveness of dialectical behavioural therapy and schema therapy in patients with borderline personality disorder: a secondary analysis of a randomised clinical trial

Abstract

Background

Borderline personality disorder (BPD) can be treated successfully with specific psychological treatments, but there is no clear evidence of superiority of one specific treatment at the group level. Due to high heterogeneity in BPD, individual patients might benefit differently from specific treatments.

Methods

Based on a randomised trial comparing 18 months of dialectical behaviour therapy (DBT) and schema therapy (ST) for BPD, differential effectiveness was examined using causal forest analyses. Baseline variables on BPD criteria, general psychopathology, traumatic childhood experiences, rejection sensitivity, level of functioning, coping skills, schemas and medication were included to predict the Borderline Personality Disorder Severity Index (BPDSI-IV) during treatment and follow-up (24 and 30 months after start of treatment).

Results

A subgroup was identified that benefited significantly more from DBT compared to ST. This group showed a significantly greater reduction in symptoms post treatment (post-treatment difference of 5.79 BPDSI points, SMD = 0.65, p = .028), but no longer at follow-up (p = .771). The group that showed better results with DBT displayed a pattern of specific baseline characteristics: higher levels of functioning, less frequent emotional neglect and sexual abuse, more severe anxiety symptoms and more pronounced schema ’failure to achieve’. No pattern of variables was identified associated with a superiority of ST.

Conclusion

Moderators of the short-term effect of DBT versus ST were found. However, this moderator effect was no longer significant at follow-up. Identifying patient characteristics associated with differential treatment effect might be a promising way to improve BPD treatment outcomes faster. Retrospectively registered (German Clinical Trials Register: DRKS00011534) without protocol changes.