Predictors of Treatment Outcome in Group or Individual Cognitive Processing Therapy for Posttraumatic Stress Disorder Among Active Duty Military

Background: The purpose of this study was to examine demographic, psychological, military, and deployment variables that might predict posttraumatic stress disorder (PTSD) symptom improvement in a sample of active duty service members who received either group or individual cognitive processing therapy (CPT). Methods: Data were analyzed from 165 active duty service members with pre- and posttreatment data participating in a randomized controlled trial comparing group with individual CPT. Pretreatment variables were examined as predictors of change in PTSD severity from baseline to posttreatment, assessed using the PTSD Symptom Scale-Interview Version (PSS-I). Predictors of PSS-I change were first evaluated using Pearson correlations, followed by partial and multiple correlations to clarify which associations remained when effects of other predictors were controlled. Multiple regression analyses were used to test for interactions between pretreatment variables and treatment format. Results: Only age was a significant predictor of PTSD symptom change after controlling for other variables and statisitically correcting for testing multiple variables. There was also an interaction between age and treatment format. Conclusions: Younger participants had greater symptom improvement, particularly if they received individual treatment. Other pretreatment variables did not predict outcome. CPT appears to be robust across most pretreatment variables, such that comorbid disorders, baseline symptom severity, and suicidal ideation do not interfere with application of CPT. However, individual CPT may be a better option particularly for younger service members.