Predicting treatment outcome on three measures for post-traumatic stress disorder.

The aim of the present study was to investigate predictors of treatment outcome for Posttraumatic Stress Disorder (PTSD) after treatment completion and at 15-months follow-up (n = 48), in a trial of Eye Movement Desensitisation and Reprocessing (EMDR) versus Imaginal Exposure and Cognitive Restructuring (E+CR). Factors associated with treatment outcome were investigated using regression analyses with the mean change scores in three assessor and self-rated PTSD symptomatology measures, including the Clinician-Administered PTSD Scale (CAPS), the Impact of Events Scale (IES) and the PTSD Symptom Checklist (PCL) from pre- to post-treatment and pre-treatment to follow-up as the dependent variables and demographics, trauma, clinical and personality measures as independent variables. Irrespective to outcome measures and assessment points it was found that four variables were able to predict significantly treatment outcome. These included baseline PTSD symptomatology, number of sessions, gender and therapy type. Overall, our results showed that it is difficult to use pre-treatment variables as a powerful and reliable tool for predicting treatment outcome, as significant predictors were found to be sample-specific and outcome measure-specific. Clinical relevance of the present results and directions for future research are discussed.