Borderline Personality Disorder (BPD) is a serious mental health condition that often co-occurs with Complex PTSD (CPTSD), making treatment more challenging. Trauma-Focused Mentalization-Based Treatment (MBT-TF) is a new adaptation of standard MBT designed for individuals with high trauma exposure. Early findings are promising, but further research is needed. This study at Geneva University Hospitals (HUG) will test the feasibility and acceptability of MBT-TF compared with standard MBT, gathering feedback from patients and clinicians and laying the groundwork for a larger clinical trial.

Borderline Personality Disorder (BPD) is a serious mental health condition that can make it difficult for people to regulate emotions and maintain relationships. Even with specialised therapy, many individuals with BPD continue to experience significant difficulties in daily life.

A large proportion of patients with BPD also show symptoms of trauma, such as Post-Traumatic Stress Disorder (PTSD) or its more complex form (CPTSD). About half of all patients with BPD meet the criteria for CPTSD, and this overlap may partly explain why standard treatments are sometimes less effective. At present, there are no clear treatment guidelines for people who have both BPD and CPTSD, even though this combination greatly affects quality of life and social functioning.

Mentalization-Based Treatment (MBT) is a structured therapy developed in the 1990s for BPD. A newer version, Trauma-Focused MBT (MBT-TF), has been designed for individuals with high levels of trauma or CPTSD. Early results from MBT-TF are promising, but further research is needed before a large-scale trial can be undertaken.

This upcoming study at Geneva University Hospitals (HUG) will examine whether MBT-TF can be delivered effectively and accepted by both patients and clinicians, compared with standard MBT ("treatment as usual"). It will also gather early evidence on whether MBT-TF may be more effective. An independent steering committee of international experts and a patient representative will oversee the trial.

Patients will be followed during 15 months, including 1 year of treatment. Patients will have to fill in questionnaires, and follow individual interviews. In total, 5 visits will be performed for the study, in addition to the stardard clinical follow-up.

Inclusion Criteria:

• Age between 18 and 65 years.
• Meeting ≥4 of 9 SCID-5 PD criteria associated with functional impairment (either subthreshold or full BPD diagnosis), and an LPFS-BF 2.0 score ≥31 (≥1.5 standard deviations above the latent mean, T-score ≥65), indicating moderate to severe personality disorder features.
• Diagnosis of CPTSD according to ICD-11 criteria, confirmed via ITQ with clinical checks.

Exclusion Criteria:

• Mental disability.
• Severe psychiatric psychopathology requiring immediate treatment (e.g., BMI <16.5, acute bipolar episode, current psychosis).
• Severe active substance dependence.
• Severe physical health problems (e.g., severe cardiovascular conditions). Severe neurological disorder.