Thin Evidence of Cannabis Pain Relief Benefits Despite Popular Medical and Recreational Use: Study

A federally funded study reviewing research on cannabis has found very little concrete evidence on its benefits as a chronic pain reliever, despite popular media and academic coverage of its medicinal potential.“With so much buzz around cannabis-related products, and the easy availability of recreational and medical marijuana in many states, consumers and patients might assume there would be more evidence about the benefits and side effects,” said lead author Dr. Marian S. McDonagh. Cannabis has been marketed as a pain reliever for years, marketed as a replacement for opioid drugs prescribed to chronic pain patients. However, researchers examined more than 3,000 studies and found only a total of 25 studies had scientifically valid evidence on its benefits for acute pain with no valid studies supporting them as chronic pain analgesics. The systematic review (pdf) found no strong evidence that cannabis and cannabinoids—molecules derived from cannabis are suitable replacements as chronic pain drugs, only finding some short-term benefits that came with adverse effects. “We saw only a small group of observational cohort studies on cannabis products that would be easily available in states that allow it, and these were not designed to answer the important questions on treating chronic pain,” said McDonagh. However, the researchers did find evidence to support a short-term benefit in treating nerve pain involving two FDA-approved synthetic products named dronabinol (traded under Marinol) and nabilone. The two drugs are also 100 percent in tetrahydrocannabinol (THC)—a major psychoactive cannabinoid that can also cause dependency—and both products also lead to significant side effects including sedation and dizziness. Another product, a spray applied under the tongue containing equal parts tetrahydrocannabinol and cannabidiol—the two major cannabinoids—known as nabiximol, also showed evidence of some clinical benefit for neuropathic pain. However, the product is not available in the United States. Nabiximol, due to its strong dosage, also came with side effects, such as nausea, sedation, and dizziness; but the researchers found drugs with low dosages had no significant impacts on pain at all. The writers found that for some cannabis products such as whole-plant ones, the findings are “sparse with imprecise estimates of effect and studies had methodological limitations,” with varied outcomes, making findings unreliable. These findings on cannabis as a whole would make it very difficult for clinicians to guide patients on how the drugs should be taken. “Cannabis products vary quite a bit in terms of their chemical composition, and this could have important effects in terms of benefits and harm to patients,” said co-author Dr. Roger Chou. “That makes it tough for patients and clinicians since the evidence for one cannabis-based product may not be the same for another.” The growing market for medical cannabis came as recent studies found opioids to only have moderate to low effects on chronic pain. Experts are also concerned on the dependency the drugs may cause, however the cannabis review has indicated that the studies on the drug are far behind opioids in demonstrating its efficacy in chronic pain. Co-author Dr. Devan Kansagara said that their study is “exactly the type of resource clinicians need to clarify for patients the areas of potential promise, the cannabis formulations that have been studied and, importantly, the major gaps in knowledge.” “Additional studies are needed to clarify the effect size estimates and our confidence in the findings,” the authors concluded. “We plan to continue to monitor the evidence on this topic on a regular basis to identify important new evidence as it emerges.” Since 2022, medical marijuana has been legalized in 37 states, with more than 5,450,000 patients estimated to be eligible for medical marijuana. Around 18 percent of Americans are estimated to take cannabis for recreational use.