Impact of Self-Reported Cannabis Use on Veterans' Intensive PTSD Treatment Outcomes

Objective: The impact of cannabis use on evidence-based posttraumatic stress disorder (PTSD) treatment outcomes remains inconclusive. Further, few studies to date have examined these relationships in intensive PTSD treatment settings, with existing literature being similarly inconclusive. The present study assessed the role of cannabis use frequency prior to and concurrent with treatment on self-reported PTSD and depressive symptoms in two samples of veterans undergoing distinct (3-week and 2-week) Cognitive Processing Therapy-based intensive treatment programs (ITPs; N3-week = 488; N2-week = 253). Method: Cannabis use frequency over the past 2 weeks was self-reported by veterans. PTSD and depression symptoms were assessed before, during, and following the ITP using the PTSD Checklist for the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition and Patient Health Questionnaire-9, respectively. Linear mixed-effects models were used to analyze the effect of cannabis use frequency prior to and concurrent with treatment on PTSD and depressive symptom change over time. Results: Individuals in the 3- and 2-week ITPs reported low rates of cannabis use prior to and concurrent with treatment. Across models, frequency of cannabis use was not significantly related to PTSD symptoms over time. Findings surrounding the impact of cannabis use on depressive symptom severity were only found in the 2-week ITP and not replicated in the 3-week ITP. Conclusion: Infrequent and/or recreational cannabis use frequency prior to or concurrent with treatment did not meaningfully impact intensive PTSD treatment outcomes. Findings associated with concurrent use need to be interpreted with caution due to the small subsample. Future research should explore whether more frequent cannabis use and the dosage differentially impact PTSD treatment outcomes.