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Living Systematic Review on Cannabis and Other Plant-Based Treatments for Chronic Pain: 2022 Update

Comparative Effectiveness Review, No. 250

Investigators: , M.D., FACP, , M.A., , B.A., , Ph.D., , M.D., M.C.R., , M.D., M.P.H., , M.D., M.S., and , Ph.D.

Rockville (MD): Agency for Healthcare Research and Quality (US); .
Report No.: 22-EHC042

Structured Abstract

Objectives:

To update the evidence on benefits and harms of cannabinoids and similar plant-based compounds to treat chronic pain using a living systematic review approach.

Data sources:

Ovid® MEDLINE®, PsycINFO®, Embase®, the Cochrane Library, and SCOPUS® databases; reference lists of included studies; and submissions received after Federal Register request were searched to April 4, 2022.

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 (SOE). 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 comparable THC to CBD ratio, high-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 a synthetic product. We conducted meta-analyses using the profile likelihood random effects model and assessed between-study heterogeneity using Cochran’s Q statistic chi square test and the I2 statistic. Magnitude of benefit was categorized as no effect or small, moderate, and large effects.

Results:

From 3,283 abstracts, 21 RCTs (N=1,905) and 8 observational studies (N=13,769) assessing different cannabinoids were included; none evaluated kratom. Studies were primarily short term, and 59 percent enrolled patients with neuropathic pain. Comparators were primarily placebo or usual care. The 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=39%; SOE: moderate) and overall function (6 RCTs, N=616, 0 to 10 scale, MD −0.42, 95% CI −0.73 to −0.16, I2=32%). 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, 31.0% vs. 8.0%, relative risk [RR] 3.57, 95% CI 2.42 to 5.60, I2=0%; sedation: 6 RCTs, N=866, 8.0% vs. 1.2%, 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 1.19 to 2.77, 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, 0 to 10 scale, MD −1.15, 95% CI −1.99 to −0.54, I2=48%; sedation: 3 RCTs, N=335, 19% vs. 10%, RR 1.73, 95% CI 1.03 to 4.63, I2=28%; nausea: 2 RCTs, N=302, 12.3% vs. 6.1%, RR 2.19, 95% CI 0.77 to 5.39; I²=0%). We also 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=40%). 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); outcomes assessing benefit were not reported or insufficient. 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=58%; SOE: moderate). Evidence (including observational studies) on whole-plant cannabis, topical or oral CBD, low-THC to CBD, other cannabinoids, comparisons with active products or between cannabis-related 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) with high- and comparable THC to CBD ratio extracted cannabinoids and synthetic products during short-term treatment (1 to 6 months); high-THC to CBD ratio products were also associated with increased risk of withdrawal due to adverse events. Evidence for whole-plant cannabis and other comparisons, outcomes, and plant-based compounds was 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

Prepared for: Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services, 5600 Fishers Lane, Rockville, MD 20857; www.ahrq.gov Contract No. 75Q80120D00006 Prepared by: Pacific Northwest Evidence-based Practice Center, Portland, OR

Suggested citation:

Chou R, Wagner J, Ahmed AY, Morasco BJ, Kansagara D, Selph S, Holmes R, Fu R. Living Systematic Review on Cannabis and Other Plant-Based Treatments for Chronic Pain: 2022 Update. Comparative Effectiveness Review No. 250. (Prepared by Pacific Northwest Evidence-based Practice Center under Contract No. 75Q80120D00006.) AHRQ Publication No. 22-EHC042. Rockville, MD: Agency for Healthcare Research and Quality; September 2022. DOI: https://doi.org/10.23970/AHRQEPCCER250UPDATE2022. 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. Most AHRQ documents are publicly available to use for noncommercial purposes (research, clinical or patient education, quality improvement projects) in the United States, and do not need specific permission to be reprinted and used unless they contain material that is copyrighted by others. Specific written permission is needed for commercial use (reprinting for sale, incorporation into software, incorporation into for-profit training courses) or for use outside of the U.S. If organizational policies require permission to adapt or use these materials, AHRQ will provide such permission in writing.

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.

A representative from AHRQ served as a Contracting Officer’s Representative and reviewed the contract deliverables for adherence to contract requirements and quality. AHRQ did not directly participate in the literature search, determination of study eligibility criteria, data analysis, interpretation of data, or preparation or drafting of this report.

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: Annual Update 1, by the Evidence-based Practice Center Program at the Agency for Healthcare Research and Quality (AHRQ).

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