Can Interpersonal Trust Predict and Account for Symptom Change During Group Cognitive Processing Therapy for PTSD? An Investigation of the Iterated Trust Game.

Abstract

Objective: Group cognitive processing therapy (GCPT) is frequently utilized to treat PTSD within the VA healthcare system, but its mechanisms are not well understood. Interpersonal trust could be an important change process in GCPT given its relevance to group-based therapy and its role in CPT, but self-report measures are inadequate for capturing the dynamic interplay that defines interpersonal trust. Here, we examined the degree to which interpersonal could predict and account for PTSD symptom change in GCPT using the iterated trust game (ITG)-a behavioral task used to approximate real-world trust behavior.

Methods: Participants were Veterans with PTSD who participated in an effectiveness trial comparing a 12-week course of GCPT (n = 37) to a treatment-as-usual (TAU) waitlist condition (n = 23) of equivalent length. Both groups completed the ITG and measures of PTSD before and after treatment as well as a pencil-paper measure of interpersonal trust before treatment. Participants in GCPT completed measures of PTSD severity, group relationship quality, and therapist relationship quality at each treatment session.

Results: Pre-post changes in ITG-measured trust behavior did not differ between GCPT and TAU (p = 0.075). However, improvements in ITG scores partially accounted for decreased PTSD symptoms in GCPT, as demonstrated by a more modest change in PTSD symptoms when ITG was in, b = -5.95, p = 0.032, versus not in the model, b = -9.05, p = 0.001. Additionally, higher ITG scores, but not self-reported trust, predicted steeper reductions in PTSD symptoms, b = -0.50, p = 0.042, and improvements in group relationship quality, b = 0.28, p = 0.037, across GCPT sessions.

Conclusions: Interpersonal trust improvement may predict and account for symptom change in GCPT. Targeting interpersonal trust during GCPT could render the treatment more effective.