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Living Systematic Review on Cannabis and Other Plant-Based Treatments for Chronic Pain
Comparative Effectiveness Review, No. 250
Investigators: Marian S. McDonagh, Pharm.D., Jesse Wagner, M.A., Azrah Y. Ahmed, B.A., Rongwei Fu, Ph.D., Benjamin Morasco, Ph.D., Devan Kansagara, M.D., M.C.R., and Roger Chou, M.D., FACP.
Structured Abstract
Objectives:
To evaluate the evidence on benefits and harms of cannabinoids and similar plant-based compounds to treat chronic pain.
Data sources:
Ovid® MEDLINE®, PsycINFO®, Embase®, the Cochrane Library, and SCOPUS® databases, reference lists of included studies, submissions received after Federal Register request were searched to July 2021.
Review methods:
Using dual review, we screened search results for randomized controlled trials (RCTs) and observational studies of patients with chronic pain evaluating cannabis, kratom, and similar compounds with any comparison group and at least 1 month of treatment or followup. Dual review was used to abstract study data, assess study-level risk of bias, and rate the strength of evidence. Prioritized outcomes included pain, overall function, and adverse events. We grouped studies that assessed tetrahydrocannabinol (THC) and/or cannabidiol (CBD) based on their THC to CBD ratio and categorized them as high-THC to CBD ratio, comparable THC to CBD ratio, and low-THC to CBD ratio. We also grouped studies by whether the product was a whole-plant product (cannabis), cannabinoids extracted or purified from a whole plant, or synthetic. We conducted meta-analyses using the profile likelihood random effects model and assessed between-study heterogeneity using Cochran’s Q statistic chi square and the I2 test for inconsistency. Magnitude of benefit was categorized into no effect or small, moderate, and large effects.
Results:
From 2,850 abstracts, 20 RCTs (N=1,776) and 7 observational studies (N=13,095) assessing different cannabinoids were included; none of kratom. Studies were primarily short term, and 75 percent enrolled patients with a variety of neuropathic pain. Comparators were primarily placebo or usual care. The strength of evidence (SOE) was low, unless otherwise noted. Compared with placebo, comparable THC to CBD ratio oral spray was associated with a small benefit in change in pain severity (7 RCTs, N=632, 0 to10 scale, mean difference [MD] −0.54, 95% confidence interval [CI] −0.95 to −0.19, I2=28%; SOE: moderate) and overall function (6 RCTs, N=616, 0 to 10 scale, MD −0.42, 95% CI −0.73 to −0.16, I2=24%). There was no effect on study withdrawals due to adverse events. There was a large increased risk of dizziness and sedation and a moderate increased risk of nausea (dizziness: 6 RCTs, N=866, 30% vs. 8%, relative risk [RR] 3.57, 95% CI 2.42 to 5.60, I2=0%; sedation: 6 RCTs, N=866, 22% vs. 16%, RR 5.04, 95% CI 2.10 to 11.89, I2=0%; and nausea: 6 RCTs, N=866, 13% vs. 7.5%, RR 1.79, 95% CI 1.20 to 2.78, I2=0%). Synthetic products with high-THC to CBD ratios were associated with a moderate improvement in pain severity, a moderate increase in sedation, and a large increase in nausea (pain: 6 RCTs, N=390 to 10 scale, MD −1.15, 95% CI −1.99 to −0.54, I2=39%; sedation: 3 RCTs, N=335, 19% vs. 10%, RR 1.73, 95% CI 1.03 to 4.63, I2=0%; nausea: 2 RCTs, N=302, 12% vs. 6%, RR 2.19, 95% CI 0.77 to 5.39; I2=0%). We found moderate SOE for a large increased risk of dizziness (2 RCTs, 32% vs. 11%, RR 2.74, 95% CI 1.47 to 6.86, I2=0%). Extracted whole-plant products with high-THC to CBD ratios (oral) were associated with a large increased risk of study withdrawal due to adverse events (1 RCT, 13.9% vs. 5.7%, RR 3.12, 95% CI 1.54 to 6.33) and dizziness (1 RCT, 62.2% vs. 7.5%, RR 8.34, 95% CI 4.53 to 15.34). We observed a moderate improvement in pain severity when combining all studies of high-THC to CBD ratio (8 RCTs, N=684, MD −1.25, 95% CI −2.09 to −0.71, I2=50%; SOE: moderate). Evidence on whole-plant cannabis, topical CBD, low-THC to CBD, other cannabinoids, comparisons with active products, and impact on use of opioids was insufficient to draw conclusions. Other important harms (psychosis, cannabis use disorder, and cognitive effects) were not reported.
Conclusions:
Low to moderate strength evidence suggests small to moderate improvements in pain (mostly neuropathic), and moderate to large increases in common adverse events (dizziness, sedation, nausea) and study withdrawal due to adverse events with high- and comparable THC to CBD ratio extracted cannabinoids and synthetic products in short-term treatment (1 to 6 months). Evidence for whole-plant cannabis, and other comparisons, outcomes, and PBCs were unavailable or insufficient to draw conclusions. Small sample sizes, lack of evidence for moderate and long-term use and other key outcomes, such as other adverse events and impact on use of opioids during treatment, indicate that more research is needed.
Contents
- Preface
- Acknowledgments
- Technical Expert Panel
- Peer Reviewers
- Evidence Summary
- Introduction
- Methods
- Results
- Description of Included Evidence
- KQ 1 and KQ 2. In adults with chronic pain, what are the benefits (KQ 1) and harms (KQ 2) of cannabinoids for treatment of chronic pain?
- KQ 3 and KQ 4. In adults with chronic pain, what are the benefits (KQ 3) and harms (KQ 4) of kratom or other plant-based substances for treatment of chronic pain?
- Discussion
- References
- Abbreviations and Acronyms
- Appendixes
- Appendix A. Literature Search Strategies
- Appendix B. Methods
- Appendix C. Included Studies List
- Appendix D. Results
- Appendix E. Evidence Tables
- Appendix F. Risk of Bias Assessment
- Appendix G. Details on Strength of Evidence
- Appendix H. Excluded Studies List
- Appendix I. Funnel Plot of High-THC Ratio Studies Included in Meta-Analysis for Pain Severity
Suggested citation:
McDonagh MS, Wagner J, Ahmed AY, Fu R, Morasco B, Kansagara D, Chou R. Living Systematic Review on Cannabis and Other Plant-Based Treatments for Chronic Pain. Comparative Effectiveness Review No. 250. (Prepared by Pacific Northwest Evidence-based Practice Center under Contract No. 75Q80120D00006.) AHRQ Publication No. 21(22)-EHC036. Rockville, MD: Agency for Healthcare Research and Quality; October 2021. DOI: https://doi.org/10.23970/AHRQEPCCER250. Posted final reports are located on the Effective Health Care Program search page.
This report is based on research conducted by the Pacific Northwest Evidence-based Practice Center (EPC) under contract to the Agency for Healthcare Research and Quality (AHRQ), Rockville, MD (Contract No. 75Q80120D00006). The findings and conclusions in this document are those of the authors, who are responsible for its contents; the findings and conclusions do not necessarily represent the views of AHRQ. Therefore, no statement in this report should be construed as an official position of AHRQ or of the U.S. Department of Health and Human Services.
None of the investigators have any affiliations or financial involvement that conflicts with the material presented in this report.
The information in this report is intended to help healthcare decision makers—patients and clinicians, health system leaders, and policymakers, among others—make well-informed decisions and thereby improve the quality of healthcare services. This report is not intended to be a substitute for the application of clinical judgment. Anyone who makes decisions concerning the provision of clinical care should consider this report in the same way as any medical reference and in conjunction with all other pertinent information, i.e., in the context of available resources and circumstances presented by individual patients.
This report is made available to the public under the terms of a licensing agreement between the author and the Agency for Healthcare Research and Quality. This report may be used and reprinted without permission except those copyrighted materials that are clearly noted in the report. Further reproduction of those copyrighted materials is prohibited without the express permission of copyright holders.
AHRQ or U.S. Department of Health and Human Services endorsement of any derivative products that may be developed from this report, such as clinical practice guidelines, other quality enhancement tools, or reimbursement or coverage policies, may not be stated or implied.
AHRQ appreciates appropriate acknowledgment and citation of its work. Suggested language for acknowledgment: This work was based on an evidence report, Living Systematic Review on Cannabis and Other Plant-Based Treatments for Chronic Pain, by the Evidence-based Practice Center Program at the Agency for Healthcare Research and Quality (AHRQ).
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