Do cannabis-based products actually help with chronic pain? - study

Despite the popularity of cannabis-based products in treating chronic pain, scientific evidence surrounding their long-term use is sorely lacking.

 A worker inspects marijuana leaves and care for plants at the Rak Jang farm, one of the first farms that has been given permission by the Thai government to grow cannabis and sell products to medical facilities, in Nakhon Ratchasima, Thailand March 28, 2021.  (photo credit: CHALINEE THIRASUPA/REUTERS)
A worker inspects marijuana leaves and care for plants at the Rak Jang farm, one of the first farms that has been given permission by the Thai government to grow cannabis and sell products to medical facilities, in Nakhon Ratchasima, Thailand March 28, 2021.
(photo credit: CHALINEE THIRASUPA/REUTERS)

Cannabis products may help treat chronic pain in the short term but can also cause other issues that were not present beforehand, a new study has found.

Researchers at Oregon Health and Science University (OHSU) sought to evaluate the benefits and harms of cannabis products used to treat chronic pain in a review of 18 placebo-controlled trials and seven cohort studies. Their findings were published in the peer-reviewed Annals of Internal Medicine.

Opioids and other medications that doctors have historically prescribed to treat chronic pain do little to achieve their goal and frequently cause negative side effects. As a result, the medical community has begun to explore other medication options including cannabis, creating the background for this review. 

In order to carry out their research and collect data, the team created a new scheme of categorization that compared products based on the ratio of tetrahydrocannabinol (THC) and cannabidiol (CBD) contained within them. 

Cannabis may help in the short term

 Pharmicists supply patients with prescribed medical marijuana at the 'Tikun Olam' store in Tel Aviv, on April 10, 2016.  (credit: HADAS PARUSH/FLASH90) Pharmicists supply patients with prescribed medical marijuana at the 'Tikun Olam' store in Tel Aviv, on April 10, 2016. (credit: HADAS PARUSH/FLASH90)

The review, which was funded by the Agency for Healthcare Research and Quality of the US Department of Health and Human Services, concluded that oral synthetic products featuring a high ratio of THC-to-CBD, as well as extracted cannabis products with comparable THC-to-CBD ratios, may lead to short-term improvements in chronic pain while also creating an increased risk of dizziness and sedation.  

Synthetic cannabis products with a high THC-to-CBD ratio were found to be associated with moderate pain alleviation and an increased risk of sedation.

In contrast, sublingual cannabis spray with a comparable THC-to-CBD ratio led to smaller improvements in the severity of pain and significantly increased the risk of sedation and dizziness while moderately increasing the risk of nausea. The latter product additionally showed improved sleep outcomes in four of the five reviewed studies that examined it.

When studying products with a low THC-to-CBD ratio, the researchers could not find sufficient evidence to draw any conclusions. 

Lacking in data

Despite the researchers' findings, the review concluded that further studies are required to evaluate the long-term outcomes of using cannabis products to treat chronic pain.

The OHSU researchers found that only 25 of the 3000 scientific studies they searched contained scientifically valid evidence. 

Marian S. McDonagh, Pharm.D. and emeritus professor of medical informatics and clinical epidemiology at the OHSU’s School of Medicine expressed her surprise at the lack of evidence surrounding cannabis products.

“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," she said in an interview with the university's newspaper.

The professor explained that, on the contrary, “there is very little scientifically valid research into most of these products. 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.

This fact is alarming given that medical and recreational marijuana is legal in over twenty states, meaning that millions of Americans have access to cannabis products that have not been sufficiently studied. 

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,” Roger Choue, M.D., one of the review’s co-authors told OHSU News. “That makes it tough for patients and clinicians, since the evidence for one cannabis-based product may not be the same for another.”

Furthermore, the researchers cannot be sure about the statistical significance or the magnitude of their findings due to the limitations of the individual studies they reviewed in addition to other factors.

With all of the uncertainty around cannabis products, Dr. McDonagh advises those suffering from chronic pain to exercise caution. “If you want to consider cannabis, you need to talk to your doctor.”