Lagged Effects of Substance Use on PTSD Severity in a Randomized Controlled Trial With Modified Prolonged Exposure and Relapse Prevention

Objective: To advance understanding of the effectiveness of evidence-based treatments for comorbid posttraumatic stress disorder (PTSD) and substance use disorder (SUD), research must provide a more nuanced picture of how substance use affects change in PTSD symptoms over the course of treatments and whether prolonged exposure techniques can be efficacious during active substance use. A data set that included patients with PTSD/subthreshold-PTSD and SUD treated with an exposure-based intervention provided an opportunity to conduct a secondary analysis to test how patients' substance use impacted PTSD change over treatment. Method: We applied growth models to week-to-week PTSD symptom and substance use changes during treatment and follow-up of a randomized controlled trial of two cognitive-behavioral treatments for PTSD and SUD: Concurrent Treatment of PTSD and SUD Using Prolonged Exposure (COPE) and Relapse Prevention Therapy (RPT). Cross-lagged analyses were used to determine whether prior week substance use impacted subsequent PTSD symptom severity. Results: Both treatments evidenced significant reductions in PTSD symptom severity. In the context of continued substance use, results suggest that individuals still benefit from exposure-based treatment. Conclusion: Results provide evidence that RPT and COPE both led to significant reductions in PTSD, providing further support that exposure-based techniques tailored for SUD can be conducted without jeopardizing PTSD or SUD outcomes. Implications for clinical decision making around treatment selection are discussed. What is the public health significance of this article? Study findings provide important support for three main points: (a) both RPT and COPE were associated with significant reductions in PTSD symptom severity for those with PTSD and SUD, (b) exposure-based techniques can be accomplished in patients with SUD regardless of frequency of use during treatment, and (c) for those who use daily during treatment, substance-use-focused-only treatment may not provide enough support to reduce PTSD symptom severity.