Post‐traumatic stress disorder as a moderator of transdiagnostic, residential eating disorder treatment outcome trajectory

Objective Residential treatment for severe eating disorders (EDs) is associated with primarily positive outcomes. However, less is known about the moderators of treatment response. Comorbid post‐traumatic stress disorder (PTSD) diagnosis is associated with increased ED symptom severity. This study investigated whether PTSD moderated outcomes of transdiagnostic, residential ED treatment based upon the Unified Protocol. Method Female patients (N = 1055) in residential ED treatment completed a clinical interview to assess PTSD diagnosis and self‐reported ED, depression, and anxiety symptoms, anxiety sensitivity, experiential avoidance, and mindfulness. We tested whether PTSD moderated trajectories of symptom change from treatment admission to discharge and 6‐month follow‐up using multilevel models. Results PTSD moderated change in ED symptoms, depression severity, and experiential avoidance. Patients with PTSD showed steeper symptom improvements from admission to discharge. However, PTSD was associated with greater symptom recurrence after residential treatment. Conclusions Patients with comorbid PTSD demonstrated more improvement during residential treatment, but experienced steeper posttreatment symptom recurrence.