In the first randomized placebo-controlled trial of smoked cannabis for PTSD in veterans, all groups improved significantly but none of the three active cannabis preparations outperformed placebo.
Veterans considering cannabis for PTSD, PTSD researchers, clinicians advising patients about cannabis for trauma symptoms
No active cannabis preparation outperformed placebo for PTSD symptoms
What the researchers found
Three cannabis preparations (high THC, high CBD, and balanced THC+CBD) were all well tolerated and all groups showed significant PTSD symptom improvement, but no active treatment was statistically better than placebo after three weeks of use.
Why it matters
Despite widespread veteran use of cannabis for PTSD, this first rigorous trial found no evidence that smoked cannabis outperforms placebo. The strong placebo response complicates future trial design.
The numbers in context
80 participants in Stage 1; 74 in Stage 2; high THC (~12% THC, <0.05% CBD); high CBD (11% CBD, 0.50% THC); THC+CBD (~7.9% THC, 8.1% CBD); placebo (<0.03% THC)
How the study worked
Double-blind, cross-over design with 80 veterans randomized to three weeks of active treatment or placebo in Stage 1, then re-randomized to a different active treatment in Stage 2 after a 2-week washout. Primary outcome was change in PTSD symptom severity.
What this study cannot tell us
Brief 3-week treatment period, difficulty blinding smoked cannabis (participants may detect active vs placebo), relatively small sample, cross-over design may introduce carryover effects.
How to read the evidence
Randomized placebo-controlled crossover trial, though limited by small size and short duration
When this study was published
Published in 2021. This landmark trial established that rigorous cannabis-for-PTSD research is feasible.
The bigger picture
The strong placebo response across all groups raises questions about whether expectation effects drive much of the reported benefit of cannabis for PTSD, a finding with implications for both research design and clinical practice.
Questions still open
- Would longer treatment periods show different results? Can smoked cannabis trials ever be adequately blinded? Would different cannabis formulations or delivery methods show superiority over placebo?
Common questions
Does smoked cannabis help PTSD?
Were different cannabis types tested?
Read the original research
The short-term impact of 3 smoked cannabis preparations versus placebo on PTSD symptoms: A randomized cross-over clinical trial.
PloS one, 16(3), e0246990
Citation
Bonn-Miller, Marcel O; Sisley, Sue; Riggs, Paula; Yazar-Klosinski, Berra; Wang, Julie B; Loflin, Mallory J E; Shechet, Benjamin; Hennigan, Colin; Matthews, Rebecca; Emerson, Amy; Doblin, Rick. (2021). The short-term impact of 3 smoked cannabis preparations versus placebo on PTSD symptoms: A randomized cross-over clinical trial.. PloS one, 16(3), e0246990. https://doi.org/10.1371/journal.pone.0246990
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