June 8, 2022 -- Good news for cannabis consumers in chronic pain: New research says the drug may relieve chronic pain as effectively as opioids and other commonly used treatments. But dizziness is common, and long-term safety is still up in the air, say the authors of the study.

The findings aren’t conclusive, and the researchers cautioned that much remains unknown about the potential risks of cannabis and its long-term effects on the body. But they said the results appear to show that both synthetic and plant-based forms of the substance are at least moderately effective at reducing pain.

Marian S. McDonagh, PharmD, of Oregon Health & Science University, in Portland, said cannabis products appear to be on par with other pain therapies, although the evidence for cannabis is weaker.

“The average reduction in pain severity is also similar to some other treatments, but we do not have studies directly comparing these treatments to draw conclusions,” said McDonagh, whose group reported their results in the Annals of Internal Medicine.

The authors evaluated cannabinoids’ ability to relieve chronic pain in several studies, nothing that their own methods and findings are distinct from those of other related research. To do this, McDonagh and her colleagues conducted what scientists call a meta-analysis, gathering previously published research on cannabis for the treatment of chronic pain to come up with an average result.

After excluding low-quality studies, they were left with 25 rigorous trials involving nearly 15,000 people. Of those, 18 were so-called randomized controlled trials, studies in which one group of patients receives a treatment and another receives sham, or placebo, therapy. Randomized controlled trials are considered the gold-standard for clinical research.

The studies included both synthetic cannabis products and plant forms of the drug. They also covered products with both tetrahydrocannabinol (THC), the main psychoactive molecule in cannabis, and CBD, another molecule in the substance that does not have mind-altering effects.

Synthetic products with high THC-to-CBD ratios were linked with moderate improvements in pain, whereas plant-based products with comparable THC-to-CBD ratios offered less relief, wrote McDonagh.

But according to Kevin F. Boehnke, PhD, and Daniel J. Clauw, MD, of the anesthesiology department and Chronic Pain and Fatigue Research Center at the University of Michigan Medical School in Ann Arbor, patients with chronic pain may face resistance, or even risk of being reported, when asking about cannabis-based products.

“Some physicians cite lack of data as rationale for not engaging with patients who wish to use or currently use cannabis,” Boehnke and Clauw wrote in an accompanying editorial. “Such practices may reflect consideration of cannabis solely as a drug of misuse (even in the 37 states where medical cannabis is legal) and requirements to refer patients who disclose or test positive for cannabis use to addiction services or decline to refill opioid prescriptions.”

The study was supported by the Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services. The investigators disclosed no conflicts of interest.