Expectancy, Adherence, and Depression as Predictors of Therapeutic Outcome as Measured by PTSD Symptoms in Veterans with MST

BACKGROUND: The aim of this study was to explore the association between treatment outcome expectancy, adherence to treatment, and depressive symptoms on symptom reduction in the treatment of PTSD in Veterans.
SUBJECTS: Participants were female and male veterans from a large Southwestern Veterans Administration Healthcare System. A total of 129 participants were randomized to receive cognitive processing therapy (CPT) or present-centered therapy (PCT). Participants completed baseline assessments prior to starting 12 sessions of therapy.
METHODS: Data from the Clinician Administered PTSD Scale (CAPS), the PTSD Checklist (PCL), Beck Depression Inventory II (BDI-II), the 16-Item Quick Inventory of Depression Symptomatology (QIDS), Expectancy of Therapeutic Outcome (ETO), homework assigned to the participants, and the number of therapy sessions completed were used in the analysis of the hypotheses. Spearman correlations and multiple regressions were used to analyze the data
RESULTS: Both number of sessions attended in the CPT group and number of sessions attended in both groups combined were significantly associated with an improvement in depression symptoms as measured by change in the QIDS score (CPT ? = .31, both ? = .29). Attendance to sessions in the CPT group was not associated with change in the PCL score. The total average minutes spent on homework in the CPT group was significantly associated with worsening of PTSD symptoms as measured by an increase in the CAPS score (? = -.51) in one model and by an increase in the PCL score (? = -.30) in a separate model. The percent of homework assignments completed in the CPT group was significantly associated with improvement in PTSD symptoms as measured by a decrease in the CAPS score (? = .32). A significant relationship was found between outcome expectancy and the number of sessions attended in the PCT group (? = .42;.39). The relationship between baseline depression symptom level as measured by the QIDS and the total average number of minutes spent on homework fell short of significance in the CPT group, p = .07. There were no significant associations between baseline depression and treatment outcome expectancy.
DISCUSSION: Greater outcome expectancy was associated with increased attendance to sessions in the PCT group, but not in the CPT group. However, greater expectancy did not predict adherence to homework and the amount of time spend doing homework. As expected, in the CPT group as well as both groups together, greater attendance to sessions was associated with an improvement in symptoms of depression. Greater adherence to homework assignments was associated with an improvement in PTSD symptoms. Contrary to predictions however, greater time spent doing the homework was associated with a worsening of PTSD symptoms and greater depression at baseline was associated with greater time spent completing homework. Furthermore, baseline depression did not predict treatment outcome expectancy, and expectancy did not predict PTSD and depression symptoms at treatment completion.
IMPLICATIONS: A greater expectation of benefit from treatment could be an indication that an individual is motivated to change. It is possible that expectations of treatment, attendance to therapy sessions, and completing homework in between sessions, are the key to benefiting from therapy.