chronic pain

In an effort to address the opioid epidemic, a prominent goal of current research is to identify alternative treatments with equal or better benefits for pain while avoiding potential unintended consequences that could result in harms.

This 'living' systematic review assesses the effectiveness and harms of cannabis and other plant-based treatments for chronic pain conditions. For the purposes of this review, plant-based compounds (PBCs) included are those that are similar to opioids in effect and that have the potential for addiction, misuse, and serious adverse effects; other PBCs such as herbal treatments are not included. The intended audience includes policy and decision makers, funders and researchers of treatments for chronic pain, and clinicians who treat chronic pain.

The report will be updated on a quarterly basis.

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.

Importance: Although pain is among the most common symptoms reported by patients, primary care practitioners (PCPs) face substantial challenges identifying and assessing pain.

Objective: To evaluate a 2-step process for chronic pain screening and follow-up in primary care.

Design, setting, and participants: A cross-sectional study of patients with a primary care visit between July 2, 2018, and June 1, 2019, was conducted at a statewide, multisite federally qualified health center. Participants included 68 PCPs and 58 medical assistants from 13 sites who implemented the screening process in primary care, and 38 866 patients aged 18 years or older with a primary care visit during that time.

Exposures: Single-question assessment of pain frequency, followed by a 3-question PEG (pain, enjoyment of life, general activity) functional assessment for patients with chronic pain.

Main outcomes and measures: Adherence to a 2-step chronic pain screening and PEG process, proportion of patients with positive screening results, mean PEG pain severity greater than or equal to 7, and documented chronic painful condition diagnosis in patient's electronic health record between 1 year before and 90 days after screening.

Results: Of 38 866 patients with a primary care visit, 31 600 patients (81.3%) underwent screening. Mean (SD) age was 46.2 (15.4) years, and most were aged 35 to 54 years (12 987 [41.1%]), female (18 436 [58.3%]), Hispanic (14 809 [46.9%]), and English-speaking (22 519 [71.3%]), and had Medicaid insurance (18 442 [58.4%]). A total of 10 262 participants (32.5%) screened positive and, of these, 9701 (94.5%) completed the PEG questionnaire. PEG responses indicated severe pain interference with activities of daily living (PEG ≥7) in 5735 (59.1%) participants. A chronic painful condition had not been diagnosed in 4257 (43.9%) patients in the year before screening. A new chronic painful condition was diagnosed at screening or within 90 days in 2250 (52.9%) patients. Care teams found the workflow acceptable, but cited lengthy administration time, challenges with comprehension of the PEG questions, and limited comprehensiveness as implementation barriers.

Conclusions and relevance: A systematic, 2-step process for chronic pain screening and functional assessment in primary care appeared to identify patients with previously undocumented chronic pain and was feasible to implement. Patient-provided information on the frequency of pain, pain level, and pain interference can help improve the assessment and monitoring of pain in primary care.

This is the third quarterly progress report for an ongoing living systematic review on
cannabis and other plant-based treatments for chronic pain. The first progress report was
published in January 2021 and the second in March 2021. The draft systematic review was
available for public comment from May 19 through June 15, 2021, on the Agency for Healthcare
Research and Quality (AHRQ) Effective Health Care website. The systematic review synthesizes
evidence on the benefits and harms of plant-based compounds (PBCs), such as cannabinoids and
kratom, used to treat chronic pain, addressing concerns about severe adverse effects, abuse,
misuse, dependence, and addiction.
The purpose of this progress report is to describe the cumulative literature identified thus far.
This report will be periodically updated with new studies as they are published and identified,
culminating in an annual systematic review that provides a synthesis of the accumulated
evidence.