Cannabis Use During PTSD Treatment Didn't Predict Worse Outcomes or Dropout in Veterans
Among 183 veterans in treatment for co-occurring PTSD and substance use, ongoing cannabis use did not predict worse PTSD symptoms or treatment dropout at subsequent assessments — though concurrent heavy drinking did.
Quick Facts
What This Study Found
A major clinical question for therapists treating veterans with both PTSD and addiction: does ongoing cannabis use during treatment sabotage the results? This secondary analysis of a randomized clinical trial with 183 veterans provides a reassuring — if nuanced — answer.
Substance use was measured at 4-week intervals throughout treatment. The researchers tested whether the percentage of days using alcohol, cannabis, or other substances at one time point predicted PTSD symptoms or treatment dropout at the next time point. The finding: cannabis use did not prospectively predict worse PTSD symptoms or treatment discontinuation.
Alcohol told a different story. When a veteran's drinking days increased by about one standard deviation (34.7% more drinking days), PTSD symptoms during that same period were measurably higher. But even alcohol didn't predict future PTSD worsening — the relationship was concurrent, not prospective.
Other substance use (primarily cocaine and opioids) also showed no prospective relationship with PTSD outcomes or dropout.
This is a clinically important null finding. It suggests that requiring cannabis abstinence as a precondition for PTSD treatment — a stance some programs take — may not be justified by the evidence. Veterans who continue using cannabis during treatment still appear to benefit from the therapy at similar rates.
Key Numbers
183 veterans. 4-week measurement intervals throughout treatment. Cannabis use: no prospective association with PTSD symptoms or dropout. Alcohol: concurrent association with worse PTSD symptoms (1 SD increase in drinking days = measurably higher PTSD symptoms in same period). No prospective associations for any substance class with treatment discontinuation.
How They Did This
Secondary analysis of a randomized clinical trial with 183 U.S. military veterans (53.8% Black, 41.9% White, 92.4% male) treated for co-occurring PTSD and substance use disorder. Substance use (percentage of days using alcohol, cannabis, other substances; average drinks per drinking day), PTSD symptoms, and treatment discontinuation measured at 4-week intervals. Multilevel models accounted for nested longitudinal data structure. Tested both concurrent and prospective associations.
Why This Research Matters
Many PTSD treatment programs require or strongly encourage abstinence from all substances before starting trauma-focused therapy. This study challenges that approach for cannabis specifically — ongoing use didn't derail treatment. For the 33% of PTSD patients who also use cannabis (RTHC-00117), this data supports engaging them in treatment as-is rather than delaying until abstinence is achieved.
The Bigger Picture
This is the veteran-specific complement to RTHC-00117 (meta-analysis finding cannabis users still benefit from PTSD therapy). Both studies reach the same conclusion from different angles: cannabis use doesn't prevent PTSD treatment from working. Combined with RTHC-00125 (psychological inflexibility as the mechanism linking CUD and PTSD), the clinical picture is becoming clearer — the problem isn't cannabis use per se, but whether it's being used as an avoidance strategy that increases psychological rigidity.
What This Study Doesn't Tell Us
Secondary analysis — not designed to test this specific question. Predominantly male veteran sample (92.4%) limits generalizability to women and civilian populations. Cannabis use measured by days of use, not dose, potency, or product type. The 4-week intervals may miss shorter-term fluctuations in use and symptoms. Null findings don't prove cannabis use is harmless during treatment — only that it didn't predict worse outcomes in this sample at this measurement frequency.
Questions This Raises
- ?Would higher-frequency or higher-dose cannabis use show different results?
- ?Does the type of cannabis product matter (high-THC vs. balanced THC:CBD)?
- ?Would these findings hold in civilian populations and with different therapy modalities?
- ?Is the concurrent alcohol-PTSD association relevant for clinical decision-making about what substances to prioritize addressing first?
Trust & Context
- Key Stat:
- Evidence Grade:
- Secondary analysis of an RCT with longitudinal measurements. The multilevel modeling approach is appropriate for the data structure, but as a secondary analysis, the study wasn't powered specifically for these comparisons. The null finding for cannabis is consistent with RTHC-00117 but needs dedicated prospective testing.
- Study Age:
- Published in 2024. The question of substance use during PTSD treatment remains actively debated in clinical practice.
- Original Title:
- The impact of substance use on posttraumatic stress disorder symptoms and treatment discontinuation.
- Published In:
- Journal of traumatic stress, 37(2), 257-266 (2024) — The Journal of Traumatic Stress is a well-respected journal that publishes research on trauma and stress-related disorders.
- Authors:
- Stevenson, Brittany L, Lee, Jenny Y, Oslin, David W, Polusny, Melissa A, Kehle-Forbes, Shannon M
- Database ID:
- RTHC-05734
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Read More on RethinkTHC
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Cite This Study
https://rethinkthc.com/research/RTHC-05734APA
Stevenson, Brittany L; Lee, Jenny Y; Oslin, David W; Polusny, Melissa A; Kehle-Forbes, Shannon M. (2024). The impact of substance use on posttraumatic stress disorder symptoms and treatment discontinuation.. Journal of traumatic stress, 37(2), 257-266. https://doi.org/10.1002/jts.23002
MLA
Stevenson, Brittany L, et al. "The impact of substance use on posttraumatic stress disorder symptoms and treatment discontinuation.." Journal of traumatic stress, 2024. https://doi.org/10.1002/jts.23002
RethinkTHC
RethinkTHC Research Database. "The impact of substance use on posttraumatic stress disorder..." RTHC-05734. Retrieved from https://rethinkthc.com/research/stevenson-2024-the-impact-of-substance
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.