Trauma-focused and personality disorder treatment for posttraumatic stress disorder and comorbid cluster C personality disorder: a randomized clinical trial.

Background: Posttraumatic stress disorder (PTSD) is associated with high rates of cluster C personality disorders (PD), which may negatively affect PTSD treatment. It is unknown whether concurrent treatment for PTSD and comorbid PD leads to superior treatment effects, compared to standard trauma-focused treatment.Objective: The objective was to test the efficacy of adding personality disorder treatment (group schema therapy; GST) to individual trauma-focused treatment (imagery rescripting; ImRs).Method: A two-arm randomized clinical trial (1:1 allocation ratio) was conducted between 2018 and 2023 at two sites of a mental health institution in the Netherlands. Raters were blind to treatment allocation. Adult outpatients with PTSD and comorbid cluster C personality disorders were randomized to receive either ImRs (12-18 sessions) or ImRs + GST (12-18 ImRs + 52-58 GST). The main outcome was PTSD severity one year after start of treatment measured with the Clinician-Administered PTSD Scale for DSM-5.Results: Of 130 patients (mean [SD] age = 40.6 [11.2], 110 [85%] females), 66 were assigned to ImRs and 64 to ImRs + GST. At 12 months, there were large decreases in PTSD severity (dImRs = 2.42, 95%CI = 1.97-2.87; dImRs + GST = 2.44, 95%CI = 1.99-2.90), but there was no significant difference between conditions (d = 0.02, 95%CI = -0.33-0.36, p = .944). Reductions in personality disorder symptoms and all other secondary outcomes were observed in both conditions. There were no significant differences between conditions on any of the secondary outcomes at 12 months.Conclusion: The more intensive concurrent trauma-focused and personality disorder treatment (ImRs + GST) was not superior to trauma-focused treatment alone (ImRs) for patients with PTSD and comorbid CPD. This suggests that trauma-focused treatment is the preferred primary treatment in patients presenting with both internalizing personality disorder and PTSD, reserving the stepping up to more intensive psychotherapy aimed at the personality disorder as a second line of treatment.Trial registration: ClinicalTrials.gov identifier: NCT03833531.