Treatment Moderators of Symptom Severity in Psychotherapy for People with Borderline Personality Disorder: Systematic...

Borderline personality disorder (BPD) is a complex and heterogeneous condition. Psychotherapy reduces symptom severity; however, characteristics of the individual may influence treatment outcomes. This systematic review examined whether specific baseline variables moderate the effect of psychotherapy on BPD severity through individual participant data meta-analysis (IPD-MA).

A literature search up to 12 May 2025 across 10 databases (including PubMed, Medline, Embase, PsycINFO, CINAHL, Web of Science, and Cochrane CENTRAL) identified randomised clinical trials (RCTs) comparing psychotherapy to treatment as usual (TAU) or clinical management control interventions (CM) for BPD. Authors of included trials were contacted to retrieve IPD. IPD-MAs employed a one-stage random-effects approach to estimate treatment effects and potential moderators in bivariate linear mixed-effects models. The study was registered with PROSPERO (CRD42021210688).

Out of 33,696 records identified, 42 RCTs (3,848 participants) were eligible. IPD was obtained from 19 trials (1,482 participants). All trials had an overall high risk of bias or some concerns regarding risk of bias. There was a high rate of missing data across trials (378/1,482, 25.1%). IPD-MA showed that psychotherapy significantly reduced BPD severity compared to TAU/CM (β: -0.25, 95% CI: -0.43 to -0.07, SE: 0.09, p = 0.0065; 19 trials, 1,104 participants). Significant negative moderators were co-occurring depressive disorder(s) (β: 0.31, 95% CI: 0.03 to 0.59) and exposure to sexual trauma (β: 0.60, 95% CI: 0.16 to 1.04), while positive moderators were co-occurring anxiety disorder(s) (β: -0.34, 95% CI: -0.64 to -0.03) and alcohol use disorder(s) (AUD) (β: -0.34, 95% CI: -0.67 to -0.01).

Psychotherapy may be especially beneficial for BPD with co-occurring anxiety. Patients with co-occurring AUD should not be excluded from treatment; rather, treatment motivation should be emphasised. Further, clinicians should prioritise trauma-informed care.