Quality-controlled cannabis for non-cancer pain is quite safe
Nine pages on PainSci cite Ware 2015: 1. Pain & Injury Survival Tips 2. The Complete Guide to Low Back Pain 3. The Complete Guide to Chronic Tension Headaches 4. The Complete Guide to Neck Pain & Cricks 5. Smoking and Chronic Pain 6. Complete Guide to Frozen Shoulder 7. A Rational Guide to Fibromyalgia 8. Marijuana for Pain 9. Weed works for pain—major new report
PainSci notes on Ware 2015:
Although we already have many reasons to suspect that cannabis usage is very safe, the more data the better on this topic, and particularly in the context of treating non-cancer pain. The results are good news, and completely consistent with other evidence. Ars Technica:
Almost every news story one reads about the use of cannabis as a medical therapy contains some variation of disclaimer saying ‘more research is needed’ into the longterm safety of medical cannabis use. Now a tiny bit of that ‘more research’ has been published in the Journal of Pain. The headline result was that there was NO INCREASE IN THE NUMBER OF SERIOUS ADVERSE EVENTS in a group that used cannabis for chronic pain when compared to a group that did not.
It’s hard to overstate how significant that kind of safety level is for any medication that helps with pain. Even the mildest over-the-counter analgesics come with serious risks (see How risky are NSAIDS?). Cannabis is not risk free — this study did find evidence of non-serious adverse events — but the total absence of serious adverse events is a big deal.
(By the way, this science comes from Canada, which is where I come from. You’re welcome.)
original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
Cannabis is widely used as a self-management strategy by patients with a wide range of symptoms and diseases including chronic noncancer pain. The safety of cannabis use for medical purposes has not been systematically evaluated. We conducted a prospective cohort study to describe safety issues among subjects with chronic noncancer pain. A standardized herbal cannabis product (12.5% THC) was dispensed to eligible subjects for a one-year period; controls were subjects with chronic pain from the same clinics who were not cannabis users. The primary outcome consisted of serious adverse events (SAEs) and non-serious adverse events (AEs). Secondary safety outcomes included pulmonary and neurocognitive function and standard hematology, biochemistry, renal, liver and endocrine function. Secondary efficacy parameters included pain and other symptoms, mood, and quality of life. Two hundred and sixteen individuals with chronic pain were recruited to the cannabis group (141 current users and 58 ex-users) and 215 controls (chronic pain but no current cannabis use) from seven clinics across Canada. The median daily cannabis dose was 2.5g/d. There was no difference in risk of SAEs (adjusted IRR=1.08, 95% CI=0.57-2.04) between groups. Medical cannabis users were at increased risk of non-serious AEs (adjusted IRR=1.73, 95% CI=1.41-2.13); most were mild to moderate. There were no differences in secondary safety assessments. Quality-controlled herbal cannabis, when used by cannabis-experienced patients as part of a monitored treatment program over one year, appears to have a reasonable safety profile. Longer term monitoring for functional outcomes is needed.
PERSPECTIVE: This study evaluated the safety of cannabis use by patients with chronic pain over one year. The study found that there was a higher rate of adverse events among cannabis users compared to controls but not for serious adverse events at an average dose of 2.5g herbal cannabis per day.
related content
- “The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research,” {The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research}, NationalAcademies.org.
- “The Effects of Cannabis Among Adults With Chronic Pain and an Overview of General Harms: A Systematic Review,” Nugent et al, Annals of Internal Medicine, 2017.
- “[Evidence of the efficacy and safety of cannabis medicines for chronic pain management: A methodological minefield],” Häuser et al, Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz, 2019.
Specifically regarding Ware 2015:
This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:
- Long-Term Effects of Repeated Injections of Local Anesthetic With or Without Corticosteroid for Lumbar Spinal Stenosis: A Randomized Trial. Friedly 2017 Arch Phys Med Rehabil.
- Cannabis-based medicines for chronic neuropathic pain in adults. Ateş 2026 Cochrane Database Syst Rev.
- Effect of exercise on depression and anxiety symptoms: systematic umbrella review with meta-meta-analysis. Munro 2026 Br J Sports Med.
- Optimizing elastic band resistance training for Metabolic Syndrome components in older adults: A systematic review, meta-analysis, and meta-regression of randomized controlled trials. Saez-Berlanga 2026 Arch Phys Med Rehabil.
- Biomechanical insights into Achilles tendinopathy risk and protection in runners: a large prospective study 4HAIE. Jandacka 2026 Br J Sports Med.