Veterans who used cannabis before or during intensive PTSD treatment programs showed similar symptom improvement to non-users — cannabis use didn't appear to undermine treatment effectiveness.
PTSD treatment providers deciding on cannabis use policies, veterans wondering if cannabis use disqualifies them from treatment, program administrators setting eligibility criteria.
What the researchers found
Across two samples of veterans undergoing Cognitive Processing Therapy-based intensive treatment programs (3-week program: N=488; 2-week program: N=253), researchers examined whether cannabis use frequency before or during treatment affected PTSD and depression outcomes.
Veterans in both programs reported low rates of cannabis use overall. The central finding was that cannabis use frequency — whether measured before treatment or concurrently — was not significantly associated with different trajectories of PTSD or depression symptom improvement over time.
Both cannabis-using and non-using veterans showed significant reductions in PTSD (measured by PCL-5) and depressive symptoms (measured by PHQ-9) from pre- to post-treatment. The treatment appeared to work regardless of cannabis use status.
This finding held across both the 3-week and 2-week program formats, providing replication across two independent samples with slightly different treatment intensities.
Why it matters
Some treatment programs exclude or discourage cannabis-using patients, and clinicians may worry that cannabis use undermines evidence-based PTSD therapy. This study provides reassurance that cannabis use at the levels observed didn't appear to interfere with intensive treatment — meaning cannabis-using veterans shouldn't necessarily be excluded from these programs.
The numbers in context
Two samples: N=488 (3-week ITP) and N=253 (2-week ITP). Cannabis use frequency not significantly associated with PTSD or depression symptom change trajectories. Both users and non-users showed significant symptom improvement on PCL-5 and PHQ-9.
How the study worked
Observational study of two veteran samples in Cognitive Processing Therapy-based intensive treatment programs (N=488 for 3-week; N=253 for 2-week). Cannabis use frequency self-reported over past 2 weeks. PTSD measured by PCL-5, depression by PHQ-9, assessed before, during, and after treatment. Linear mixed-effects models analyzed cannabis use frequency effects on symptom trajectories.
Who was studied
N=741 veterans, mixed gender, undergoing intensive PTSD treatment in the US.
What this study cannot tell us
Low overall rates of cannabis use in these samples may have limited statistical power to detect effects. Self-reported cannabis use likely underestimates actual use in a treatment setting. Observational design — cannabis-using and non-using veterans may differ in unmeasured ways. Intensive treatment programs are a specific context; results may not generalize to standard outpatient PTSD therapy.
How to read the evidence
Observational study with two independent replication samples — strengthened by consistency across both programs but limited by low cannabis use rates and observational design.
When this study was published
Published in 2026, addressing a practical clinical question relevant to the growing overlap between cannabis use and PTSD treatment seeking.
The bigger picture
This study presents an interesting contrast with the abstinence study (RTHC-00274), which found that quitting cannabis produced larger PTSD improvements. The key difference: this study asked whether cannabis use undermines treatment (answer: no), while the abstinence study asked whether quitting cannabis enhances improvement (answer: possibly yes). Both can be true — cannabis may not prevent therapy from working, but quitting might allow it to work even better. The veteran harm reduction study (RTHC-00267) adds the patient perspective on why veterans continue using during treatment.
Replication
Not stated in abstract.
Funding
Not reported in abstract.
Conflicts of interest
Not reported in abstract.
Questions still open
- Would heavier cannabis use (not captured in these low-use samples) interfere with treatment more than light use? Could cannabis use actually enhance treatment engagement for some veterans by reducing avoidance? Is there a level of cannabis use above which treatment outcomes start to diverge?
Read the original research
Impact of self-reported cannabis use on veterans' intensive PTSD treatment outcomes.
Psychological trauma : theory, research, practice and policy, 18(3), 628-637
Psychological Trauma is a reputable journal focusing on trauma research and its implications for practice.
Citation
Schubert, Ryan A; Splaine, Cailan C; Montes, Mauricio M; Pridgen, Sarah A; Kaysen, Debra L; Held, Philip. (2026). Impact of self-reported cannabis use on veterans' intensive PTSD treatment outcomes.. Psychological trauma : theory, research, practice and policy, 18(3), 628-637. https://doi.org/10.1037/tra0001842
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