An investigation of outcome expectancies as a predictor of treatment response for combat veterans with PTSD: comparison of clinician, self-report, and biological measures.

BACKGROUND: Outcome expectancy, or the degree to which a client believes that therapy will result in improvement, is related to improved treatment outcomes for multiple disorders. There is a paucity of research investigating this relation in regards to posttraumatic stress disorder (PTSD). Additionally, the bulk of the research on outcome expectancy and treatment outcomes has relied mostly on self-report outcome measures. METHODS: The relation between outcome expectancy on self-report measures, clinician-rated measures, and two biological indices (fear-potentiated startle and cortisol reactivity) of PTSD symptoms was explored. The sample included combat veterans (N = 116) treated with virtual reality exposure therapy for PTSD. RESULTS: Results supported a negative association between outcome expectancy and both self-report and clinician-rated symptoms at the conclusion of treatment, but outcome expectancy was related to the magnitude of change during treatment for self-report measures only. Outcome expectancy was unrelated to biological measures of treatment response. CONCLUSIONS: These findings suggest that outcome expectancy may be related to patient and clinician perceptions of outcomes, but not biological indices of outcome for PTSD.