Mentalization based treatment for a broad range of personality disorders: a naturalistic study

Several studies have observed that mentalization-based treatment (MBT) is an effective treatment for borderline personality disorder (BPD), but its effectiveness for other personality disorders (PDs) has hardly been examined. Additionally, the evidence supporting the claim that MBT improves mentalizing capacity is scarce. The present study examined whether (i) patients with a broad range of PDs enrolled in an MBT program would improve on several outcome measures (ii) mentalizing capacity would improve over time; (iii) patients with BPD would improve more than those with non-borderline PDs.

Personality disorders, psychiatric symptoms, social functioning, maladaptive personality functioning and mentalizing capacity were measured in a group of individuals with various PDs (n = 46) that received MBT. Assessments were made at baseline and after 6, 12, and 18 months of treatment. The severity of psychiatric symptoms, measured using the Outcome Questionnaire 45, was the primary outcome variable.

Overall, enrollment in the MBT program was associated with a decrease in psychiatric symptoms and an improvement of personality functioning, social functioning for a mixed group of PDs (all p's $$ .01). Bigger effect sizes were observed for BPD patients (n = 25) than for patients with non-BPD (n = 21), but the difference failed to reach statistical significance (p = 0.06). A primary analysis showed that the decrease in psychiatric symptoms was significant in BPD patients (p = 0.01), not in non-BPD (p = 0.19) patients. However, a sufficiently powered secondary analysis with imputed data showed that non-BPD patients reported a significant decrease in psychiatric symptoms too (p = 0.01). Mentalizing capacity of the whole group improved over time (d = .68 on the Toronto Alexithymia Scale and 1.46 on the Social Cognition and Object Relations System).

These results suggest that MBT coincides with symptomatic and functional improvement across a broad range of PDs and shows that MBT is associated with improvements in mentalizing capacity. As the study is not experimental in design, we cannot make causal claims.

Mentalization-based treatment may be an effective treatment for patients with a broad range of PDs.

The study design was approved by the Leiden University Ethical Committee.