In a controlled trial in veterans, smoked cannabis did not reduce PTSD symptoms more than a placebo.
A 2021 randomized trial tested whether any of three smoked cannabis preparations reduced PTSD symptoms more than a placebo, in military veterans.
Eighty U.S. military veterans with PTSD took part in a double-blind trial comparing three types of smoked cannabis (high-THC, high-CBD, and a mix) against a placebo over three weeks. On the main measure of PTSD symptoms, none of the cannabis types did any better than the placebo. Notably, everyone improved over the three weeks — including the placebo group — and all were generally well tolerated. It's an important, sobering result given how many veterans use cannabis to self-treat PTSD: in a controlled test, the benefit looked like a placebo response rather than a specific effect of cannabis.
This double-blind, placebo-controlled cross-over trial randomized U.S. military veterans with PTSD (Stage 1 N=80) to three weeks of one of three active smoked cannabis preparations (High THC ~12%, High CBD ~11%, or THC+CBD ~8%/8%) or placebo. The primary outcome was change in PTSD symptom severity over Stage 1. There was no significant difference between any active cannabis concentration and placebo; all groups, including placebo, showed significant symptom improvement and good tolerability.
This is one of the few randomized, placebo-controlled tests of smoked cannabis for PTSD, which makes the negative result informative. The strong placebo-group improvement underscores how expectancy and repeated assessment can produce apparent benefit in uncontrolled settings. Limitations include the short three-week window, the cross-over design, and the focus on smoked whole-plant cannabis at fixed concentrations — it does not address other formulations, doses, or long-term use.
Given widespread self-medication with cannabis for PTSD among veterans, this trial is an important controlled counterpoint to observational reports of benefit. It stands alongside other rigorously controlled military trials that did not confirm a hoped-for effect — for example, repeated ketamine infusions that did not beat placebo on PTSD (Abdallah et al., 2022).
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