Determining the median effective dose of prolonged exposure therapy for veterans with posttraumatic stress disorder

Prolonged exposure therapy (PE) is an effective treatment for posttraumatic stress disorder (PTSD). Identifying metrics of treatment response can guide treatment delivery. The median effective dose represents the number of sessions at which there is a 50% probability of clinically meaningful improvement (i.e., 10-point reduction in PTSD checklist). The goal of the current study was to investigate the median effective dose of PE. We identified a cohort of Iraq and Afghanistan war veterans who received psychotherapy for PTSD in the Veterans Health Administration between 2001 and 2017. From this cohort, 10,234 veterans who received PE (as identified using natural language processing) and had ≥2 PTSD symptom measures were included in analyses. To determine how the number of PE sessions and covariates affected clinically meaningful improvement, we utilized a Cox proportional hazards regression, followed by Kaplan-Meier curves to determine the median effective dose. The median effective dose of PE was four sessions. Although some covariates were found to be statistically significant predictors of clinically meaningful improvement (e.g., age, gender, PTSD medications, and depressive disorder comorbidity), these effects were small. Clinicians and patients should consider evaluating treatment response after four sessions to determine preliminary effectiveness of PE.