Little Evidence Cannabis Can Treat Chronic Pain

By Roger Chriss, Columnist

There is an abundance of research on medical cannabis. Everything from basic science to clinical trials and even major reviews have been conducted on the effectiveness of cannabis in treating chronic pain and other conditions. But the results don’t necessarily say what people want to hear.

As Leafly shows in a comprehensive list, most states in the U.S. that have legalized medical cannabis include chronic pain or painful conditions among the accepted indications for use. But these same states also note that research supporting medical cannabis for chronic pain is thin.

Minnesota, for example, accepts “intractable pain” but then says that “the literature assessing the effects of medical cannabis treatments for non-cancer chronic pain is sparse and patchy.”

Similarly, the California Medical Association’s “Physician Recommendation of Medical Cannabis” states that the approved list of 12 serious medical conditions that cannabis can be used for “is broad, and in most cases not supported by solid clinical research.”

In other words, medical cannabis has been approved for use, despite having not been rigorously demonstrated to be useful.

The existing research supports this view. A recent systematic review of two dozen clinical trials published in the journal Pain Physician found that “the majority of studies did not show an effect.” The review concludes that cannabis-based medications “might be effective for chronic pain treatment, based on limited evidence, primarily for neuropathic pain (NP) patients.”

Another recent review of randomized placebo-controlled studies of smoked cannabis published in the journal Pharmacotherapy found that “cannabis did not outperform placebo on experimentally evoked pain.”

And a systematic review of the efficacy of cannabis in patients with neuropathic pain, multiple sclerosis or receiving  chemotherapy concluded that “there is incomplete evidence of the efficacy and safety of medical use of cannabis” and that “confidence in the estimate of the effect was again low or very low.”

Even reviews of medical cannabis for disorders that involve a chronic pain component are lackluster. A 2017 systematic review looked at randomized controlled trials of cannabis and its derivatives in treating psychiatric, movement, and neuro-degenerative disorders. The review found that "definitive conclusion on its efficacy could not be drawn” because the trials were low quality and had methodological limitations.

These results run contrary to the public perception of cannabis efficacy and the exuberance of media coverage about marijuana in any form. This has not escaped the notice of researchers. A 2017 study from Europe found that “public perception of the efficacy, tolerability, and safety of cannabis-based medicines in pain management and palliative medicine conflicts with the findings of systematic reviews and prospective observational studies conducted according to the standards of evidence-based medicine.”

Moreover, the Pain Physician study notes another significant trend: More recent studies tend to report more favorable results. It is not clear why this is happening, though a shift in cultural attitudes, ongoing advocacy in favor or cannabis legalization, and changes in the available strains of cannabis have been suggested. In particular, an increasingly positive attitude toward cannabis among study participants may be augmenting the placebo effect.

There are other limitations to the existing research -- from problems with blinding, lack of a good placebo and small study size – that make it open to criticism. Much of the commentary on cannabis research seems to have less to do with a close reading of the literature than with a desire for cannabis to gain widespread acceptance.

There is, of course, growing evidence for the use of cannabis in the treatment of some disorders, such as epilepsy and chronic neuropathic pain.  Medical cannabis may also have some value for people who are not benefiting from or cannot tolerate pharmaceutical drugs and other established therapies. So cannabis should remain an option -- intractable pain is sufficiently horrible that we need as many options as possible.

Medical research is about accumulating evidence through clinical trials and laboratory study. One trial is rarely ever enough to demonstrate efficacy. Even one major review is not sufficient. But an abundance of reviews all pointing in one direction should not go ignored.

Medical cannabis certainly merits further study. But the above reviews clearly show that efficacy is limited in many cases. Cannabis may well prove useful in treating certain disorders, but it is not a panacea and not likely to outperform existing treatments.

Roger Chriss lives with Ehlers Danlos syndrome and is a proud member of the Ehlers-Danlos Society. Roger is a technical consultant in Washington state, where he specializes in mathematics and research.

The information in this column should not be considered as professional medical advice, diagnosis or treatment. It is for informational purposes only and represents the author’s opinions alone. It does not inherently express or reflect the views, opinions and/or positions of Pain News Network.