A first-of-its-kind federal review of studies on cannabis for pain shows mild to moderate relief from pain, but “moderate to large increases” in common adverse events like dizziness and sedation. And, evidence on whole-plant cannabis was “insufficient,” as was the “impact on use of opioids.”
On March 18, the Agency for Healthcare Research and Quality, one of a dozen agencies within the U.S. Department of Health and Human Services (DHHS), released its first annual update for its Living Systematic Review on Cannabis and Other Plant-Based Treatments for Chronic Pain. The ongoing systematic review is focused on “cannabis and other plant-based treatments for chronic pain.”
The Agency initiated the review in late 2020, writing that the “challenges of treating chronic pain in light of the lackluster evidence on opioids, the ongoing opioid crisis, and difficulty in safely prescribing opioids drive a search for alternative pain treatments, including cannabis.” Its first draft systematic review was published in January of this year.
This first annual update included 21 randomized controlled trials and 8 observational studies, and patients had chronic pain that was mostly neuropathic and could be treated in a relatively short window of time (between four weeks and six months).
Studies were gathered based on tetrahydrocannabinol (THC) to cannabidiol (CBD) ratio, for example: high-THC to CBD, similar ratios of THC to CBD, and low-THC to CBD (including solely CBD). Researchers also added a new placebo-controlled randomized controlled trial that included oral CBD, and a new observational study that examined a plant-based solution of 1:1 THC to CBD, compared to the addition of synthetic CBD.
There is “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 in short-term treatment,” which is one to six months, the review concluded. Regarding high-THC to CBD ratio products, they were “associated with increased risk of withdrawal” because of common adverse events like dizziness, when compared to the placebo.
Researchers found that evidence related to whole-plant cannabis was either unavailable or “insufficient to draw conclusions, despite some new evidence for oral CBD and comparing cannabis-based products.”
The review concluded with yet another call for more research: “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.”
The update is open for public comment until April 22.
