The most common medical reason for which people report using CBD is to manage chronic pain, followed closely by managing arthritis or joint pain. But does it actually work?

When the National Academies of Sciences, Medicine, and Engineering evaluated decades of cannabis research, they concluded that "in adults with chronic pain, patients who were treated with cannabis or cannabinoids are more likely to experience a clinically significant reduction in pain symptoms."

But that’s not quite as exciting for CBD as it sounds: “We don’t know cannabidiol’s effects on its own,” says Ziva Cooper ⁽¹⁾, who was part of the National Academies committee that put together this report. “[The conclusions about cannabis and cannabinoids] were based on what we know about THC or THC plus cannabidiol.”

In fact, the most compelling research they found for using cannabinoids for pain came from a large review and meta-analysis published in JAMA in 2015. For the study, researchers looked at results from 79 previous studies of cannabinoids and various medical conditions, including chronic pain. However, of those studies, only four involved CBD (without THC)—none of which were looking at pain. So although we might assume that CBD is doing something to help address pain—according to the studies involving the whole cannabis plant—we don’t have great evidence to prove it.

“It might be that cannabidiol by itself is helpful for pain, but at this point we don’t know that,” Cooper says.

The studies we do have about CBD for pain are all animal studies. For example, in a 2017 study published in Pain, researchers gave rats an injection into one of their knee joints to model osteoarthritis. Rats then either received doses of CBD or saline directly into an artery in the knee joint. Results showed that, after receiving CBD, rats showed less inflammation in the joint area and fewer pain-related behaviors (like shaking or withdrawing the affected paw or not being able to bear weight in that paw) compared to those that received saline.

Another study published in 2016 in the European Journal of Pain also looked at arthritis in rats but did so with a topical formulation of CBD. After the rats received an injection into one knee joint to model arthritis, they received a gel that contained either 10 percent CBD (in four different total amounts) or 1 percent CBD (the control) on four consecutive days. The gel was massaged into the rats’ shaved backs for 30 seconds each time.

Then the researchers measured the inflammation in each rat’s knee joint, the level of CBD that made it into their bloodstream, and their pain-related behaviors. They found that the rats that were given the two highest doses of CBD showed significantly lower levels of inflammation and lower pain behavior scores compared to those that got the control. The two lower doses didn’t show much of an effect.

But if you’re reading this, you are probably not a rat, which means these results aren’t directly applicable to your life. Although we know that rats do share much of our physiology—including CB1 and CB2 receptors—these studies don’t really tell us if humans would have the same results with CBD.

“There’s really no substitute for doing proper human studies, which are difficult, expensive, and ethically complicated,” Dr. Tishler says. And we simply don’t have them for CBD and pain.

(1) Ziva Cooper, Ph.D., research director of the UCLA Cannabis Research Initiative in the Jane and Terry Semel Institute for Neuroscience and Human Behavior and the department of psychiatry and biobehavioral sciences