Personality disorders and their relation to treatment outcomes in cognitive behavioural therapy for depression: a systematic review and meta-analysis

Background

Previous reviews indicate that depressed patients with a comorbid personality disorder (PD) tend to benefit less from psychotherapies for depression and thus personality pathology needs to be the primary focus of treatment. This review specifically focused on studies of Cognitive Behavioural Therapy (CBT) for depression examining the influence of comorbid PD on post-treatment depression outcomes.

Methods

This was a systematic review and meta-analysis of studies identified through PubMed, PsychINFO, Web of Science, and Scopus. A review protocol was pre-registered in the PROSPERO database (CRD42019128590).

Results

Eleven eligible studies (N = 769) were included in a narrative synthesis, and ten (N = 690) provided sufficient data for inclusion in random effects meta-analysis. All studies were rated as having “low” or “moderate” risk of bias and there was no significant evidence of publication bias. A small pooled effect size indicated that patients with PD had marginally higher depression severity after CBT compared to patients without PD (g = 0.26, [95% CI: 0.10, 0.43], p = .002), but the effect was not significant in controlled trials (p = .075), studies with low risk of bias (p = .107) and studies that adjusted for intake severity (p = .827). Furthermore, PD cases showed symptomatic improvements across studies, particularly those with longer treatment durations (16–20 sessions).

Conclusions

The apparent effect of PD on depression outcomes is likely explained by higher intake severity rather than treatment resistance. Excluding these patients from evidence-based care for depression is unjustified, and adequately lengthy CBT should be routinely offered.