Research on mechanisms of change in prolonged exposure therapy (PE), an evidence-based treatment for posttraumatic stress disorder (PTSD), is ongoing. Two putative mechanisms of change are engagement during imaginal exposure and trauma-related belief change. The PE Therapist Questionnaire (PETQ), a novel measure based on the emotional processing theory underlying PE, was developed as a practical tool for therapists to use to assess (a) patient engagement during imaginal exposures and (b) perspective shifts during postimaginal processing. Patients (N = 151) at a U.S. Veterans Affairs medical center PTSD specialty clinic completed self-report measures of PTSD and depression symptoms prior to sessions. Study therapists (n = 17) completed the PETQ postsession. Rational construction and psychometric analyses suggested a two-component solution for the PETQ: imaginal and processing. The imaginal factor did not relate to PTSD and depression symptoms. The processing factor correlated with current and next-session PTSD and depression symptoms, with medium effect sizes, rs = -.41 to -.45, ps < .001. Controlling for current-session PTSD and depression, a higher level of processing predicted lower next-session PTSD severity, with a small effect size, β = -.38, p < .04. Postexposure emotional processing, which supports positive changes in maladaptive trauma-related beliefs and tolerance of emotional distress, predicted future symptom improvement, highlighting the importance of processing components in PE. Further, the use of therapist observations may offer ancillary methods less influenced by correlation of within-patient subjective ratings and concomitant risk of construct overlap in mechanisms research.
© 2020 International Society for Traumatic Stress Studies.