The present study examined temporal patterns of symptom change during treatment for comorbid posttraumatic stress disorders (PTSD) and substance use disorders (SUDs). We hypothesized that PTSD symptom severity would predict subsequent-session substance use and that this association would be particularly strong among patients who received an integrated treatment versus SUD-only treatment. Participants were 81 United States military veterans with current PTSD and an SUD who were enrolled in a 12-week, randomized controlled trial examining the efficacy of an integrated treatment called Concurrent Treatment of PTSD and Substance Use Disorders Using Prolonged Exposure (COPE) compared with cognitive behavioral relapse prevention therapy (RP). Lagged multilevel models indicated that PTSD symptom improvement did not significantly predict the likelihood of next-session substance use (likelihood of use: B = 0.03, SE = 0.02, p = .141; percentage of days using B = -0.02, SE = 0.01, p = .172. Neither substance use, B = 1.53, SE = 1.79, p = .391, nor frequency of use, B = 0.26, SE = 0.50, p = .612, predicted next-session PTSD symptom severity in either treatment condition. Stronger associations between PTSD symptoms and next-session substance use were expected given the self-medication hypothesis. Additional research is needed to better understand the temporal dynamics of symptom change as well as the specific mediators and mechanisms underlying symptom change.
© 2021 International Society for Traumatic Stress Studies.