THC products offer small improvements in pain but have side effects.

THC products offer small improvements in pain but have side effects.

New systematic evidence review on cannabis products

A new systematic review of evidence shows that cannabis products containing relatively high levels of the psychoactive substance tetrahydrocannabinol, better known as THC, may provide short-term improvements in pain and function.

However, the review notes that THC-based products increase the risk of common side effects such as dizziness, sedation and nausea.

At the same time, the review showed that recent randomized controlled trials examining products containing primarily or exclusively cannabidiol (CBD), which has no psychoactive properties, demonstrated little improvement in pain management.

"This may come as a surprise to many. Previously, CBD was thought to be promising because it does not have euphoric effects like THC and was believed to have medicinal properties. But at least in our analysis, it had no effect on pain."

Roger Chou, M.D., senior author and senior adviser for the Pacific Northwest Evidence-based Practice Center at Oregon Health & Science University

What are THC and CBD?

The cannabis plant contains both THC and CBD. Both should be on that Endocannabinoid system of the body that modulates pain. Many US states, including Oregon, have legalized cannabis for both recreational and medical use. Many people use cannabis to treat conditions such as pain, anxiety and sleep disorders.

The review is an update to an ongoing review first published in 2022 and was conducted by OHSU researchers. She was in the todayAnnals of Internal Medicinepublished.

The researchers have included several additional short-term placebo-controlled randomized trials since the previous review. Both the original review and the new update found some evidence of pain relief with two prescription products, dronabinol and nabilone, which are 100% THC or its analogs. Dronabinol and nabilone are FDA-approved for the treatment of nausea and vomiting due to chemotherapy, and one of them, dronabinol, is also approved for HIV wasting syndrome.

The new review found that oral THC products slightly reduce pain severity.

Pain relief and side effects

Chou pointed out that the improvement in pain was relatively small - about between half a point to one point compared to a placebo on a 10-point pain scale.

“It’s complicated because cannabis products are complicated,” he said. "It's not like taking a standardized dose of ibuprofen. Cannabis comes from a plant and contains many different chemicals in addition to THC and CBD, which can have different properties depending on where it is grown, how it is grown and ultimately how it is prepared for sale."

The medical community is divided on the benefits of medical use of cannabis: The American College of Physicians recently recommended against recommending inhaled cannabis for non-cancer pain, while a previous expert panel made a weak recommendation for people with chronic cancer or non-cancer pain when standard treatments didn't work.

Chou said the finding that CBD products failed to relieve pain will surprise many.

"CBD-based products are widely available in pharmacies. Many people use these products and think they help," he said. “Our goal is to provide a scientific basis to help people make their decisions.”

Categorization of cannabinoids

Researchers categorized cannabinoids by the ratio of THC to CBD (whether it was high, comparable, or low); whether the product is synthetic (lab-made) or plant-based (as well as the level of purification); and the method of administration.

The data showed that oral THC products slightly reduced pain severity, but that they were also associated with moderate to severe increases in dizziness, sedation and nausea.

They concluded that more research is needed on long-term outcomes and other types of cannabis products; whether there are differences in the effectiveness of THC products; and to better understand how the results apply to the products available in pharmacies.

In addition to Chou, co-authors included Rongwei Fu, Ph.D., Azrah Y. Ahmed, B.A., and Benjamin J. Morasco, Ph.D. to the team.

Sources: