Metacognitive Interpersonal Therapy for Personality Disorders: A Case Study Series

The study aimed to assess the effectiveness of metacognitive interpersonal therapy (MIT) as a psychological treatment for presentations consistent with non-borderline personality disorders (PD). We conducted a single-case series of three patients with personality disorders meeting inclusion criteria. Clients received 2 years of weekly individual MIT. Outcomes were assessed every 3 months for the first year at the end of treatment and at 3-months follow-up. Co-primary outcomes were reduction in the number of SCID-II PD criteria met and reduction in self-reported global distress (SCL-90-R GSI). Secondary outcomes were reduction in self-reported interpersonal problems (IIP-32), anxiety (STAI-Y), depression (BDI-II) and emotional dysregulation (DERS). Reliable Change Indices were calculated for all outcomes. All three patients completed treatment, achieving reliable change at the end of treatment for reduction in total number of personality disorder criteria and in overall symptoms. For secondary outcomes, two patients improved in emotion regulation, one in depression. There was no evidence of reliable change on self-reported anxiety or interpersonal problems. At 3-months post treatment improvements in overall symptoms and emotional regulation were observed for all patients. Plot analyses of the results showed a trend towards reduction for all outcomes. MIT is a new manualized treatment for non-borderline PD’s. We demonstrate preliminary evidence of acceptability and effectiveness in this understudied population. Future studies are required to establish the effectiveness of MIT in larger PD samples, including patients with lower socio-economic status.