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Research finds that cannabis products with THC can relieve chronic pain

Researchers in Oregon trawled through 3,000 studies.

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By Danny Halpin via SWNS

Cannabis products containing the active ingredient THC do relieve chronic pain in the short term, scientists have revealed.

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Researchers recommend talking with a doctor before trying any cannabis products for pain relief. (Blue Titan/Shutterstock)

The study is one of the first to examine its pain-relieving properties despite many products being legalized and sold across the US.

Voters in Oregon, Washington and 20 other states have legalized medical and recreational marijuana, however, the researchers, from Oregon Health & Science University (OHSU), found many products available in dispensaries have not been studied.

Cannabis was legalized for medicinal use in the UK in November 2018 but since then almost no NHS prescriptions have been issued, with doctors citing a lack of placebo-controlled trials as a reason for their hesitancy.

In the federally-funded review published in the Annals of Internal Medicine, researchers trawled through 3,000 studies in the scientific literature up to January this year and found a total of 25 with scientifically valid evidence – 18 randomized controlled studies and seven observational studies of at least four weeks.

They also found there was evidence to support a short-term benefit in treating neuropathic pain such as diabetic neuropathy which causes a burning or tingling sensation when the nerves become damaged.

The drugs found to be effective were tetrahydrocannabinol, or THC, and dronabinol (brand name Marinol) with nabilone (Cesamet).

According to the review, both products also led to notable side effects, including sedation and dizziness.

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A marijuana leaf. (Toasted Pictures/Shutterstock)

Another product, an under-the-tongue spray known as nabiximols, made of equal parts THC and cannabidiol, or CBD, also appeared to treat neuropathic pain.

This also led to side effects such as nausea, sedation and dizziness.

The study’s lead author Professor Marian McDonagh, at OHSU, said: “In general, the limited amount of evidence surprised all of us.

“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.

“Unfortunately, there is very little scientifically valid research into most of these products.

“We only saw 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.”

The authors together summarised: “For some cannabis products, such as whole-plant products, the data are sparse with imprecise estimates of effects and studies had methodological limitations.”

Cannabis products are based on their ability to mimic the body’s own endocannabinoid system.

This is comprised of receptors and enzymes in the nervous system that regulate bodily functions and can affect the sensation of pain.

In the evidence review, researchers sorted the types of products into high, comparable and low ratios of THC to CBD and compared their reported benefits and side effects.

Dronabinol and nabilone fit into the high THC and CBD ratio category, with 100% THC (no CBD) showing the most benefit among the products studied.

And six of the randomized controlled studies demonstrated statistically valid benefits for easing neuropathic pain compared to a placebo.

Co-author Dr. Roger Chou, at OHSU, said: “Cannabis products vary quite a bit in terms of their chemical composition and this could have important side effects in terms of benefits and harm to patients.

“That makes it tough for patients and clinicians alike since the evidence for one cannabis-based product may not be the same for another.”

The living review includes a visual abstract summary of the findings and will also be shared on a new web-based tool launched by OHSU and VA Portland Health Care System this year to help clinicians and researchers evaluate the latest evidence on the health effects of cannabis.

Known as Systematically Testing the Evidence on Marijuana, or STEM, the project includes clinical briefs to help health care workers translate the clinical implications.

Co-author Dr. Devan Kansagara, also of OHSU, said: “This new living evidence review 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.”

Dr. McDonagh added: “Honestly, the best advice is to talk to your primary care physician about possible treatments for chronic pain.

“If you want to consider cannabis, you need to talk to your doctor.”

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