Treatment dose and reliable change in trauma-focused therapy for comorbid PTSD and MDD.

OBJECTIVE: Major depressive disorder (MDD) commonly co-occurs with posttraumatic stress disorder (PTSD) and increases risk for reduced response to evidence-based PTSD treatment, yet little is known regarding the dose-outcome link for this comorbidity. METHOD: The relationship between attendance and reliable change was examined among 88 service members with comorbid PTSD/MDD receiving cognitive processing therapy (CPT) or CPT with behavioral activation (BA + CPT) in a clinical trial. Survival analyses calculated reliable change likelihood during treatment for PTSD, MDD, and both, and explored between-treatment differences. RESULTS: Among participants reporting reliable change, median attendance equaled the full treatment protocol. Reliable change likelihood was higher when completing treatment versus adequate dose. A log-rank test comparing Kaplan-Meier curves between treatments was statistically significant for reliable change in both disorders (χ2(1) = 4.46, p = .03), but not PTSD (χ2(1) = 3.06, p = .08) or MDD (χ2(1) = 1.86, p = .17) alone. Cox proportional hazards regression indicated reliable change for both disorders was less likely in BA + CPT (hazard rate = 0.52, 95% confidence interval: 0.28, 0.97, p = .04). CONCLUSION: Results highlight differences in symptom change timing between a standard and integrated treatment and suggest strong adherence (i.e., completing protocol) is critical for this comorbidity.Trial registration: ClinicalTrials.gov identifier: NCT02874131..