In his eight seasons in the National Hockey League, Riley Cote estimates he got into hundreds of fistfights. Cote was an enforcer—a tough guy whose job was to keep the other team’s players in check. If an opponent got too physical on the ice, Cote would put him in line.He retired in 2010, having sustained repeated trauma to his brain and body. Cote suffered from chronic pain, and worried what might happen to his battered mind as he aged. Then in 2013, he tried cannabidiol, more commonly known as CBD. “It’s been a game changer for sure,” Cote says. Now he reports he uses it at least twice a day.In the wake of the opioid crisis and with a growing body of evidence showing the dangers of repeated brain injuries, cannabis and its extract cannabidiol have come to seem like promising wonder drugs that can reduce dependence on opioids. In 2017, the World Anti-Doping Agency removed CBD from its list of banned substances. That same year, former National Basketball Association commissioner David Stern said the league should change its policies to allow players to use medical marijuana. And this year, the National Football League Players’ Association partnered with the NFL to study marijuana and CBD as alternatives to other pain therapies, namely opioids.CBD, which is both not psychotropic and not addictive, has garnered several star advocates. Enthusiasts like former New York Giants receiver Tiki Barber, former Boston Celtic Paul Pierce, and recently retired New England Patriots star Rob Gronkowski all have their own CBD companies that promote the substance as a powerful healing tool that can manage pain, and in Pierce’s case, help with crippling anxiety. Their advocacy has raised the drug’s profile and helped kick off a national conversation.But is the science as convincing as their sales pitch? Scientists believe CBD is doing something to alleviate chronic pain and inflammation, but what exactly that is, and what the proper doses or best delivery methods are, remain a mystery. “Large numbers of people are seeing anecdotal benefits, so there’s something there,” says Jeffrey Raber, a chemist and CEO of the Werc Shop, a cannabis lab in California. “I don’t think we’re very close to having figured it out yet.”LEARN MOREThe WIRED Guide to CannabisLike THC, the more famous, psychoactive compound in weed, CBD is derived from marijuana or hemp. It acts on the endocannabinoid system, interacting with the CB1 and CB2 receptors all over your body that help regulate many functions including sleep, memory, appetite, pain, metabolism, and the reproductive system. CBD won’t get you high, but research on rodents suggests it might have significant curative powers.One study, for example, has found that rubbing CBD cream on the joints of arthritis-afflicted rats could help treat their ailment by reducing inflammation. Another one found that CBD could also reduce pain from osteoarthritis. Researchers showed that rats were able to bear more weight on their afflicted limbs and had less inflammation in their joints after taking CBD.Rodents, though, aren’t people. Their metabolisms work differently. They don’t suffer from the same conditions as humans. And something as complex as pain, with its many causes, is better studied in humans when possible. “We really do need more clinical trials and more research,” says Andrea Hohmann, a cannabidiol researcher at the University of Indiana who is studying CBD’s potential as a nonaddictive pain therapy.CBD intrigues her because it appears to be a relatively safe compound compared with more powerful painkillers, like oxycontin or fentanyl. Given that a significant number of retired NFL players report using opioids, a new medication option could make a big difference.The National Institutes of Health think so too. This month, the NIH announced nine new research grants devoted to investigating CBD’s potential as an anti-inflammatory and pain relief therapy.Cote, who has also started his own CBD business, bookends his days with the drug. He takes one pill in the morning to help with pain management and inflammation and a tincture at night to help him sleep. If he’s sore from a workout, he might use a topical cream during the day on his muscles or joints.But unlike over-the-counter pain meds like aspirin and ibuprofen, there is no labeled box or set of studies telling Cote how much to take. Cote had to figure that out for himself, monitoring how his body responded to different doses and delivery mechanisms. “Certainly there’s an element of self-experimentation,” he says.Also, is it just pure CBD that’s helping Cote? That’s unclear too. Nothing about these products is standardized. Some of them could be adulterated, especially in states where weed is still illegal and where there isn’t a state-run testing infrastructure. And there’s a huge amount of variation between products. Each cream, tincture, and tonic has its own unique recipe. Some include additional marijuana chemicals; others don’t. Swallowable pills made by different companies may not all have the same absorbency.“CBD is probably what one might refer to as a dirty drug,” says Hohmann, meaning that its mechanisms are highly sensitive to its environment and mode of consumption. The many other compounds in marijuana—terpenoids, THC, and others—could all affect how your body processes CBD. And genetic variation also makes people react very differently. Right now there’s no data on what formats or formulations are the most efficient, let alone safe. “We would know a lot more about it,” says Raber, “if we had not made it illegal.”For pro-CBD athletes, a more solid scientific backing could help prove out their claims and change league policies. A positive drug test in most professional sports, including the National Basketball Association and Major League Baseball, can land you in a substance abuse program along with a hefty fine. In the NFL, you could miss games or even be banned from the sport. Only the National Hockey League has stopped penalizing players who test positive for marijuana.But the leagues themselves aren’t the only hurdle: CBD still isn’t legal in every state. CBD-promoting athletes will have to do more than change league rules to get their pain reliever of choice into the mainstream. They’ll have to change national drug policies too.More Great WIRED StoriesA brutal murder, a wearable witness, and an unlikely suspectCapitalism made this mess, and this mess will ruin capitalismCleaner ships may mean more expensive holidaysThe symmetry and chaos of the world’s megacitiesAfter six years in exile, Edward Snowden explains himself👁 How do machines learn? Plus, read the latest news on artificial intelligence✨ Optimize your home life with our Gear team’s best picks, from robot vacuums to affordable mattresses to smart speakers.