Cannabinoids for Chronic Pain: Effect Sizes Are Small
What Researchers Found About Chronic Pain and Cannabis
The Study at a Glance
Published
Journal of Neuroimmune Pharmacology, 2020
Researchers
Multiple institutions (International)
Study Type
Meta-AnalysisDuration
N/A (meta-analysis of 43 RCTs)
Key Finding
Pain intensity of chronic non-cancer patients was reduced by cannabinoids consumption, but effect sizes were small. Efficacy for neuropathic and non-neuropathic pain was similar.
Key Finding: Pain intensity of chronic non-cancer patients was reduced by cannabinoids consumption, but effect sizes were small. Efficacy for neuropathic and non-neuropathic pain was similar.
What Researchers Studied About Chronic Pain and Cannabis
This was a systematic review and meta-analysis of randomized controlled trials evaluating the analgesic efficacy and adverse effects of cannabinoids for chronic non-cancer pain.
Researchers searched PubMed, EMBASE, Web of Science, Cochrane CENTRAL, and clinicaltrials.gov up to December 2018.
43 randomized controlled trials were included, with meta-analysis performed for 33 studies that compared cannabinoids to placebo.
How This Meta-Analysis Was Conducted
Information on cannabinoid type, dosage, route of administration, pain conditions, pain scores, and adverse events was extracted.
Meta-regression was performed to compare analgesic efficacy for different pain conditions (neuropathic versus non-neuropathic pain).
Risk of bias was assessed using The Cochrane Risk of Bias tool, and strength of evidence was assessed using the GRADE approach.
Chronic Pain Treatment Results
The Main Results:
- 1Mean pain score reduction (0-10 scale): -0.70 (p < 0.001)
- 2Neuropathic vs non-neuropathic pain: similar efficacy (Difference = -0.14, p = 0.262)
- 3Inhaled cannabinoids: -0.97 pain reduction (p < 0.001)
- 4Oral cannabinoids: -0.85 pain reduction (p < 0.001)
- 5Oromucosal cannabinoids: -0.45 pain reduction (p < 0.001)
- 6Serious adverse events were rare
- 7Non-serious adverse events were usually mild to moderate
- 8Heterogeneity was moderate
- 9GRADE level of evidence: low to moderate
By the Numbers
| Statistic | What It Means |
|---|---|
| 43 RCTs | Number of randomized controlled trials included in the review |
| -0.70 points | Mean pain score reduction on 0-10 scale (statistically significant but small) |
| p = 0.262 | No significant difference between neuropathic and non-neuropathic pain efficacy |
| -0.97 vs -0.45 | Inhaled cannabinoids reduced pain more than oromucosal (both p < 0.001) |
Number of randomized controlled trials included in the review
Mean pain score reduction on 0-10 scale (statistically significant but small)
No significant difference between neuropathic and non-neuropathic pain efficacy
Inhaled cannabinoids reduced pain more than oromucosal (both p < 0.001)
What This Means for Chronic Pain Patients
This large meta-analysis of 43 randomized trials has important news for chronic pain patients: cannabinoids DO reduce pain, but the effect is small.
On a 0-10 pain scale, cannabinoids reduced pain by about 0.7 points compared to placebo. While statistically significant (p < 0.001), this is a modest benefit.
Good news: cannabinoids work similarly for nerve pain and other types of chronic pain. You do not need a specific pain type to potentially benefit.
How you take it matters: Inhaled cannabinoids showed the largest pain reduction (-0.97), followed by oral (-0.85), then oromucosal/spray (-0.45). All routes were statistically significant.
Safety was reasonable: serious adverse events were rare, and non-serious side effects were usually mild to moderate.
The evidence quality was low to moderate, meaning more research is needed to be more certain.
Quick Answers: Chronic Pain and Cannabis
Direct answers based on the findings of this study:
Research Summary: Answers are based on published peer-reviewed studies and represent research findings, not medical recommendations. Individual results may vary. Always consult a healthcare provider before making treatment decisions.
How effective is cannabis for chronic pain?
Yes, with small effect (0.7 points on 0-10 scale). A 2020 meta-analysis of 43 RCTs found cannabinoids reduce chronic non-cancer pain (p < 0.001). Serious adverse events were rare.
Source: Wong et al., J Neuroimmune Pharmacol, 2020 (PMID: 32172501)
Is inhaled or oral cannabis better for pain?
Inhaled cannabinoids showed the largest pain reduction (-0.97 points), followed by oral (-0.85), then oromucosal spray (-0.45). All routes were statistically significant (p < 0.001) in this meta-analysis of 43 RCTs.
Source: Wong et al., J Neuroimmune Pharmacol, 2020 (PMID: 32172501)
What is the evidence for cannabis and chronic pain?
Low to moderate quality evidence of small benefit. A meta-analysis of 43 RCTs found cannabinoids reduce chronic non-cancer pain by 0.7 points on 0-10 scale. Neuropathic and non-neuropathic pain responded similarly.
Source: Wong et al., J Neuroimmune Pharmacol, 2020 (PMID: 32172501)
This is educational content, not medical advice
The research summarized here is for informational purposes only. Individual results may vary, and what works in studies may not work the same way for everyone. Always consult with a qualified healthcare provider before making changes to your treatment plan or starting medical cannabis therapy.
Important Limitations
This study has some caveats to keep in mind when interpreting the results:
- Effect sizes were small (less than 1 point on 0-10 scale)
- GRADE evidence level: low to moderate
- Moderate heterogeneity across studies
- Data only through December 2018
- Non-cancer pain only
The Bottom Line on Cannabis for Chronic Pain
This meta-analysis of 43 RCTs found cannabinoids reduce chronic non-cancer pain, but effect sizes are small (about 0.7 points on a 0-10 scale). Inhaled cannabinoids worked best (-0.97), followed by oral (-0.85), then spray (-0.45). Neuropathic and non-neuropathic pain responded similarly. Serious side effects were rare. Evidence quality: low to moderate.
Do You Qualify for Medical Marijuana?
If you're living with Chronic Pain, you may qualify for a medical marijuana card. Our licensed physicians can evaluate you from home via telehealth.
Related Research & Resources
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Source
Wong SSC, Chan WS, Cheung CW "Analgesic Effects of Cannabinoids for Chronic Non-cancer Pain: a Systematic Review and Meta-Analysis with Meta-Regression" Journal of Neuroimmune Pharmacology. 2020. DOI: 10.1007/s11481-020-09905-y
Important Information
Study Age: This study was published 6 years ago. Newer research may have updated or refined these findings.
Not Medical Advice: This research summary is for educational purposes only. It should not be used to diagnose, treat, cure, or prevent any disease or medical condition. Always consult a qualified healthcare provider before starting or changing any treatment.
Individual Variation: Research findings represent group averages. Your individual response to cannabis may differ based on genetics, other medications, underlying conditions, and many other factors.
Last reviewed: January 25, 2026
Important Notices
Research Summary Disclaimer
This content represents our interpretation of published scientific research for educational purposes. It should not be used to make treatment decisions without consulting a qualified healthcare provider. Individual results may vary from study findings.
FDA Notice
These statements have not been evaluated by the FDA. Cannabis is not intended to diagnose, treat, cure, or prevent any disease. The FDA has not approved cannabis for any medical condition except specific prescription medications.
Copyright & Fair Use
Research summaries are provided under fair use (17 U.S.C. § 107) for educational purposes. We provide brief summaries with attribution, not full reproductions. All studies remain the intellectual property of their respective authors and publishers.
Data Sources
Study information sourced from PubMed®, U.S. National Library of Medicine. Inclusion does not imply endorsement by NLM, NIH, or the federal government.
For complete information, see our Terms of Use and Research Content Policy.
FAQs: Cannabis for Chronic Pain
How much does cannabis reduce chronic pain?
Small but significant benefit. A meta-analysis of 43 RCTs found cannabinoids reduce pain by about 0.7 points on a 0-10 scale. This is statistically significant but represents a small effect size.
Does cannabis work better for nerve pain?
No. Meta-regression found no significant difference between neuropathic and non-neuropathic pain (p = 0.262). Cannabinoids work similarly for both types.
What is the best way to take cannabis for pain?
Inhaled cannabinoids showed the largest pain reduction (-0.97), followed by oral (-0.85), then oromucosal spray (-0.45). All routes were statistically significant (p < 0.001).