Study Finds Cannabis Increases Pain Tolerance

By Steve Weakley

Medical marijuana is often touted as a promising new form of pain relief.  But a new study found that cannabinoids may not reduce pain as much as they increase our tolerance of pain and make it less unpleasant.

Researchers at Syracuse University conducted a systematic review of 18 placebo-controlled studies involving nearly 450 participants who used a wide variety of cannabis products, including plant-based marijuana and two synthetic marijuana-based drugs, dronabinol and nabilone.

Because most previous cannabis studies have only examined patients with chronic pain, which is often associated with depression, anxiety and other symptoms that could bias results, the researchers only selected studies that used healthy individuals and laboratory tests that induced “experimental” pain.  

They reported in the journal JAMA Psychiatry that cannabinoids did not reduce pain intensity, but made the experimental pain “feel less unpleasant and more tolerable.”

"If you think of pain as a noxious sound coming from a radio, the volume is the intensity of that pain," researcher Martin De Vita told MedPage Today. "After using cannabinoid drugs, it may not decrease the volume of the noxious noise, but it may tune it to a station that's a little less unpleasant. It won't be the most beautiful music you've ever heard -- it will still be pain -- but it will be a little less unpleasant.”

Researchers found that relatively high cannabinoid dosages improved pain tolerance, but low doses had little or no effect.  The plant-based marijuana was also more effective at reducing pain than the synthetic pharmaceuticals drugs, which are primarily used to prevent nausea.

De Vita says findings from the 18 placebo-controlled studies are somewhat compromised because patients getting the plant-based cannabis “felt high,” while those getting placebo did not. He said future studies need to test non-psychoactive cannabinoids like cannabidiol, which do not have tetrahydrocannabinol (THC), the substance in marijuana that causes euphoria.

"Everyone is saying we need more research and that we need to catch up," De Vita said. "This is a first step in doing that, starting from the fundamentals of how cannabinoids affect basic pain processes, and now we need to determine some of these follow-up questions." 

This is not the first study to get mixed results on the effectiveness of cannabis in treating pain. A recent Australian study of over 1,500 adults with chronic pain, published in The Lancet Public Health, found "no evidence that cannabis use improved patient outcomes.”

But a 2017 report by the National Academies of Sciences (NAS) found “substantial evidence” that cannabis is an effective treatment for chronic pain. The NAS found that “cannabinoids demonstrate a modest effect on pain.”