Cannabis & Chronic Pain in Veterans — Evidence Review
Chronic pain affects approximately 60% of returning Middle East deployment veterans. The evidence for cannabis in chronic pain is the strongest of any indication reviewed on this site — but strongest does not mean strong. NASEM rated it "conclusive or substantial," but the VA's own review found only "low-strength" evidence for plant cannabis in neuropathic pain.
The Honest Summary
NASEM 2017 gave chronic pain its highest evidence rating. But most trials studied pharmaceutical cannabinoids (nabiximols, nabilone, dronabinol), not the plant cannabis veterans access. The VA's Nugent et al. review found only low-strength evidence for plant cannabis in neuropathic pain. Benefits are modest; NNT ~3.4 in the best data; NNH ~6. For every 24 patients treated, one achieves 30% pain reduction, and 4 experience adverse events.
NASEM 2017: The Highest Evidence Rating
The National Academies of Sciences, Engineering, and Medicine (NASEM) 2017 report gave chronic pain its highest evidence rating: "conclusive or substantial evidence that cannabis or cannabinoids are effective for the treatment of chronic pain in adults." This was one of only three therapeutic conditions receiving this top tier, alongside chemotherapy-induced nausea and MS spasticity.
Five fair-to-good quality systematic reviews and 28 RCTs with 2,454 patients supported this conclusion. However, the report acknowledged that "minor limitations, including chance, bias, and confounding factors, cannot be ruled out." And most reviewed trials studied pharmaceutical cannabinoids (nabiximols, nabilone, dronabinol), not the plant cannabis veterans actually access.
The Major Systematic Reviews
Whiting et al. 2015
The largest systematic review — 79 RCTs with 6,462 participants. For pain, cannabinoids were associated with a greater proportion of patients reporting relief: 37% vs. 31% placebo (OR 1.41, 95% CI 0.99–2.00). The weighted mean difference on a 0–10 pain scale was −0.46 points. Only 4 of 79 trials were at low risk of bias.
Nugent et al. 2017 (VA Evidence-Based Synthesis Program)
This VA Evidence-Based Synthesis Program review found "low-strength evidence that cannabis alleviates neuropathic pain but insufficient evidence in other pain populations." This more conservative conclusion reflects its focus on plant-based cannabis rather than pharmaceuticals — making it the single most directly relevant review for what veterans actually access.
Stockings et al. 2018
The most comprehensive and arguably most cautious review — 104 studies with 9,958 participants. Found a number needed to treat (NNT) of 24 for 30% pain reduction, but a number needed to harm (NNH) of 6. The pooled effect on pain intensity was a 3 mm reduction on a 100 mm scale — statistically significant but clinically tiny. For every patient achieving meaningful relief, approximately 4 patients experience adverse events.
Which Veteran Pain Conditions Have Evidence
Neuropathic Pain — Strongest Evidence
Neuropathic pain has the strongest evidence base. The Canadian Pain Society rated cannabinoids as a third-line treatment with NNT of 3.4, compared to pregabalin at 4.5 and gabapentin at 6.5. Multiple RCTs of inhaled/vaporized cannabis show modest but statistically significant reductions.
Musculoskeletal Pain — The Gap
Musculoskeletal pain is the most common veteran pain condition, but it has very limited cannabis-specific evidence. Most cannabis RCTs studied neuropathic pain; few examined back pain, knee pain, or osteoarthritis. This represents a significant gap between where the evidence is strongest and what veterans most commonly experience.
Phantom Limb Pain — Case Reports Only
Up to 85% of amputees experience phantom limb pain, and the condition is often treatment-refractory. Cannabis research is essentially limited to case reports. This is an important but under-studied area.
Fibromyalgia
Small observational studies from Israel (Habib & Artul 2018, PMID 29461346, N=26; Sagy et al. 2019, PMID 31163665, N=367) report high response rates, but without control groups. The Cochrane review (Walitt et al. 2016) found insufficient evidence.
The Opioid Substitution Question
The relationship between cannabis access and opioid use is one of the most contested areas in the field.
This ecological study found that states with medical cannabis laws had a 24.8% lower mean annual opioid overdose mortality rate. The association strengthened over time, reaching 33% by years 5–6.
But Shover et al. 2019 extended the same analysis through 2017 and found the association reversed to +23%. The authors concluded: "A more plausible interpretation is that this association is spurious." This reversal finding is essential context whenever the Bachhuber study is cited.
Found that Medicare Part D opioid prescriptions decreased by 2.11 million daily doses per year in states with medical cannabis laws. States with dispensaries showed a 14.4% reduction.
Patient-reported data (Lucas et al. 2017, PMID 28189912) found 63% of authorized Canadian medical cannabis patients reported substituting cannabis for prescription drugs, with 32% substituting for opioids.
The honest bottom line: These are population-level associations, not individual-level proof. Ecological studies cannot determine whether the same people using cannabis were those who would otherwise use or die from opioids. The Shover reversal critically undermines causal claims. Research suggests a complex relationship; research does not prove that cannabis access reduces opioid harms.
VA Opioid Prescribing Progress
VA has made substantial progress since the peak of its opioid crisis. Since the Opioid Safety Initiative launched in 2013:
- Veterans dispensed opioids decreased 56%
- Co-prescribed opioids/benzodiazepines decreased 83%
- Veterans on high-dose opioids decreased 77%
The VA/DoD 2022 Clinical Practice Guideline now recommends against initiation of opioid therapy for chronic noncancer pain. VA has invested heavily in non-pharmacological alternatives including acupuncture, chiropractic care, cognitive behavioral therapy for pain, physical therapy, Whole Health programs, and integrative medicine.
What This Means for Veterans with Chronic Pain
- Cannabis may provide modest benefit for neuropathic pain, particularly for veterans who have exhausted conventional options. The benefit is real but typically small.
- For musculoskeletal pain — the most common veteran pain — evidence is limited. Cannabis is not proven to help most common back, knee, or joint pain.
- Harms are meaningful. NNH ~6 means adverse effects are common even at modest doses. Cannabis-medication interactions matter for veterans on multiple drugs.
- Evidence-based alternatives exist and are often covered by VA. Physical therapy, CBT for chronic pain, acupuncture, and integrative approaches have growing evidence and lower side effect burdens. VA treatment options.
- If you do use cannabis for pain, tell your VA provider. They can coordinate care safely. Disclosure protections.