Extended Group Written Exposure Therapy for Comorbid PTSD and BPD (Traits)

• Group Written Exposure Therapy (Behavioral): Group Extended Written Exposure Therapy (GE-WET) is a time-limited cognitive behavioural therapy for Posttraumatic Stress Disorder (PTSD) aimed at allowing patients to process their traumatic experiences in a safe environment. GE-WET will consist of 10 weekly group sessions. Participants will be asked to complete weekly in-session written exposures where they will recount their traumatic experience. The written exposure will be followed by a guided discussion about the experience of writing the exposure. There is no homework assigned between sessions. However, group members will be asked to refrain from avoiding thinking about the trauma between sessions.

Primary outcomes

• PTSD Checklist for DSM-5 (PCL-5) [From pre-treatment (1 week before the start of group) to one-month follow-up at about 4 months]

Secondary outcomes

• Posttraumatic Cognitions Inventory [From pre-treatment (1 week before the start of group) to one-month follow-up at about 4 months]: A 36-item self-report questionnaire that assesses negative thoughts across three subscales: negative cognitions about the self (e.g., "I am a weak person"), negative cognitions about the world (e.g., "I have to be on guard all the time"), and self-blame (e.g., "the event happened because of the way I acted"). The PTCI has demonstrated good internal consistency, test-retest reliability, and convergent validity with other measures of posttraumatic cognitions.
• Borderline Symptom List- Short Version (BSL-23) [From pre-treatment (1 week before the start of group) to one-month follow-up at about 4 months]: The BSL-23 is a 23-item self-report measure that assesses for DSM borderline personality disorder symptomatology as well as associated problems such as self-criticism, loneliness, helplessness, and problems with trust. The BSL-23 has demonstrated high internal consistency and test-retest reliability, and strong convergent validity with correlations with depression and general psychopathology severity.
• Borderline Symptom List Behaviour Supplement [From pre-treatment (1 week before the start of group) to one-month follow-up at about 4 months]: The BSL-23 Behaviour Supplement is an 11-item supplemental measure used to assess frequency of problematic behaviours (e.g., non-suicidal self-injury, suicide attempts, suicidal communication, angry outbursts, misuse of substances, etc.) associated with borderline personality disorder.
• Toronto Alexithymia Scale-20 (TAS-20) [From pre-treatment (1 week before the start of group) to one-month follow-up at about 4 months]: The TAS-20 is a 20-item self-report measure assessing for alexithymia (i.e., issues in identifying and processing emotions) across three factors: difficulty identifying feelings, difficulty describing feelings, and externally-oriented thinking. The TAS-20 has demonstrated adequate levels of convergent validity, good internal consistency, and good test-retest reliability.
• Experience of Shame Scale (ESS) [From pre-treatment (1 week before the start of group) to one-month follow-up at about 4 months]: The ESS is a 25-item self-report measure assessing characterological shame (e.g., shame of personal habits or personal ability), behavioural shame (e.g., shame in doing or saying something wrong), and bodily shame (e.g., shame regarding one's body). The ESS has demonstrated good internal consistency and test-retest reliability.
• Difficulties in Emotion Regulation Scale (DERS) [From pre-treatment (1 week before the start of group) to one-month follow-up at about 4 months]: The DERS is a widely used 36-item self-report measure assessing six dimensions of emotion regulation difficulties. The DERS demonstrates good internal consistency, convergent validity, and predictive validity of behaviours reflective of emotion regulation difficulties.
• Group Cohesion Scale - Revised (GCS-R) [Mid treatment (at about 5 weeks after start of group) and post treatment (at about 10 weeks)]: The GCS-R is a self-report measure that measure's group member's perception of their group and the strength of the bonds formed. The GCS-R showed high reliability for use in research and is sensitive to detecting changes in cohesiveness as a function of group development.

Sex: All, ages: 18 Years to 65 Years

Inclusion Criteria:

* Reading and writing proficiency in English
* Access to an electronic device to attend virtual group meetings
* Age 18-65
* Previous diagnosis of Posttraumatic Stress Disorder (PTSD) and Borderline Personality Disorder (BPD)/BPD traits
* Completion of a DBT skills group via St. Joe's Community Psychiatry Clinic

Exclusion Criteria:

* Diagnosis of an active severe substance use disorder or psychotic disorder
* Untreated active psychotic symptoms, mania, or hypomania
* Has attempted suicide in the 2 months prior to treatment beginning
* Has engaged in high-risk self-harm (e.g., cutting, burning, asphyxiation) in the 2 months prior to beginning treatment
* Has completed Cognitive Processing Therapy or another active PTSD treatment (i.e., prolonged exposure) in the past year

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