Study protocol for a single-blind, parallel-group, randomized, controlled superiority trial of intensive versus weekly delivered prolonged exposure for adults with post-traumatic stress disorder.

Background: Prolonged exposure (PE) therapy is widely recognized as an effective treatment for post-traumatic stress disorder (PTSD) and is often considered one of the primary options for addressing this condition. Nevertheless, a significant proportion of patients (30-51%) fail to demonstrate clinically significant symptom changes. One of the reasons is that a high proportion of patients drop out from treatment, which often lasts for a minimum of 3-4 months. Hence, there is an urgent need for PTSD treatments that can be delivered to decrease dropout rates. A more intensive PE treatment approach has been suggested to decrease dropout rates and in addition achieve faster recovery rates and has shown promising effects on reducing PTSD symptoms but needs to be tested against firsthand treatment.

Methods: This single-blind, randomized controlled trial (N = 140) will compare an intensive delivery format of prolonged exposure (iPE) against standard weekly delivered sessions of PE. The primary outcome is change on the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5). Secondary outcomes include self-rated measures of symptoms of PTSD and complex PTSD, depression and quality of life, speed of recovery, cost effectiveness, dropout rates, and adverse events.

Discussion: This study will be the first to compare iPE with first-line treatment in a psychiatric outpatient setting. One of the key strengths of this study lies in its implementation within a clinical setting and the broad eligibility criteria. Additionally, the utilization of gold-standard assessment measures ensures the accuracy and reliability of the outcomes. However, several potential challenges may arise during the study's execution. These challenges may include difficulties in participant recruitment, ensuring adequate participant retention, adherence to the treatment protocol, and maintaining therapist retention mostly due to recruitment taking place at one single clinic.

Trial Registration Number: Clinicaltrials.gov NCT05934175. Registered on June 6, 2023. Open Science Framework (OSF) https://osf.io/7qsb3 . Registered on September 2, 2023.