When 21-year-old American star sprinter Sha’Carri Richardson was disqualified from the Summer Olympic Games in Tokyo after a positive marijuana test, it left many asking, “Should cannabis use by athletes be prohibited?”

Richardson said she used marijuana to deal with the news about the death of a parent and not to boost performance. Her exclusion has become a matter of heated debate. In making this decision, the U.S. Anti-Doping Agency (USADA) has stated that it was following the rules of the World Anti-Doping Agency (WADA), which classifies marijuana and other cannabinoids, including synthetic versions of these compounds, as banned substances in competition.  WADA prohibits substances that meet two of three criteria: posing a health risk to athletes, potentially enhancing performance or violating “the spirit of sport.”

Scientists say, however, that data supporting marijuana’s performance-enhancing effects are scant—and, if anything, that the evidence seems to point to the drug actually reducing athletic ability. And while some experts agree that it has potential harmful effects to health, others say that the research to date suggests that cannabis is not more harmful than alcohol, a substance for which WADA has much laxer rules.

“[Richardson] was doing something legal in the state that she was in for reasons that, frankly, seemed perfectly understandable—to deny her the chance to compete at the highest level just seem to me absolutely ridiculous,” says Angela Bryan, a professor of psychology and neuroscience at the University of Colorado Boulder. “I definitely think that [WADA] should take a look at more current evidence and reevaluate their position.”

Does Pot Improve Athletic Performance?

A key paper cited to explain WADA’s decision to place marijuana on the prohibited list is a 2011 review article by two members of the agency and a toxicologist at the U.S. National Institute on Drug Abuse. In it, the authors state that, based on the animal and human studies that were available at the time, “cannabis can be performance enhancing for some athletes and sports disciplines.”

Margaret Haney, a professor of neurobiology who studies the effects of cannabis at the Columbia University Irving Medical Center, says the data the authors used to support that stance in the paper are “really not impressive at all and almost contradict what they claim.” For instance, she notes, the article cites a study of cyclists that reported that endurance was slightly reduced after consuming weed.

Since 2011 there have been several published review papers in which researchers evaluated the available research on this issue. Many of them—including one co-authored by the current medical director of WADA—have come to the same conclusion: no convincing evidence exists that cannabis can make athletes better at their sports.

“I think the consensus, in the absence of clear-cut information, is that cannabis is more likely to be viewed as performance-detracting rather than performance-enhancing,” says David McDuff, a sports psychiatrist and professor at the University of Maryland, who is also a member of the International Olympic Committee’s Mental Health Workgroup. “Some studies suggest that consuming marijuana has negative effects on skills such as motor coordination and mental alertness that are required in many sports—but even there, little direct evidence exists of such effects in athletes,” McDuff adds.

In addition to the lack of robust evidence for cannabis’s performance-enhancing effects, Whitney Ogle, an assistant professor of kinesiology at Humboldt State University, says that some effects of marijuana that the 2011 paper point to as beneficial during sports, such as reduced anxiety and better sleep, are associated with cannabidiol, a substance found in marijuana that WADA removed from its prohibited list in 2018.

There is some anecdotal evidence suggesting that cannabis use before a workout is fairly common—although what that means for performance is unclear. A few years ago, Bryan and her colleagues carried out an online survey of approximately 600 people living in U.S. states where marijuana is legal, and around 70 percent of them reported using the drug shortly before exercise. Ogle’s research, also based on online surveys, suggests that smoking weed before exercise helps athletes stay motivated and makes the experience more enjoyable. Some even claim it helps their performance. But whether any beneficial effect exists—or if people are simply perceiving themselves as performing better under the influence of marijuana—is unknown, Ogle adds.

One big caveat of many of the studies on cannabis and athletic performance that have been done to date, Ogle says, is that the THC levels in the products investigated are much lower than what’s found in products that have become available in recent years. Researchers have conducted this research primarily with cannabis containing less than 5 percent THC, while the commercially available strains today can contain around 30 percent THC or more. Since most of the available evidence is based on products with a very low percent of THC, it’s hard to extrapolate those findings to the products on the shelf today, Ogle says.

Should Weed Be Banned?

Even if marijuana is not performance-enhancing, WADA can justify the ban on the ground that it poses a danger to athletes’ health and safety and that it violates the spirit of sport, which includes a long list of values that should be maintained by a competitor, such as honesty, dedication and respect for rules and laws. “You don‘t actually need to focus on performance to meet two of the three criteria,” McDuff says, explaining that the case for the latter can be made because cannabis use is still illegal in most countries that participate in international sporting events such as the Olympics. When it comes to health, “the evidence is pretty clear that there are adverse health risks from the use of cannabis, especially regular daily use,” he adds. “I do think we should err on the side of [marijuana] being on a list until the evidence is crystal clear that it should be off the list.”

The potential harms of cannabis can come in many forms, McDuff says. They include a greater risk of accidents—as suggested by reports of the drug impairing driving abilities—and psychosis in a subset of individuals predisposed to the disorder and cannabis addiction. Some studies suggest addiction occurs in around 9 percent of users, with people who start using the drug at an early age facing the greatest risk.

Other experts, however, say that while such risks are real, it is unfair to apply a double standard to marijuana when alcohol—a substance that is not included in WADA’s prohibited list—has similar, if not worse, adverse effects. “Alcohol is something that’s far riskier in cannabis use for health, in terms of morbidity and mortality,” Bryan says. “I think [cannabis] should be treated like other drugs that people use for various reasons—alcohol, caffeine, nicotine. It should be regulated, but I don’t think it should be banned.”

Debate around this issue comes at a somewhat unique time in recent history. Attitudes toward marijuana have drastically shifted in the past few years, as has been illustrated by the legalization of recreational cannabis in several states and the entire country of Canada. And many other nations around the world are considering permitting use of the drug for medical and leisure purposes.

This has resulted in changes within professional sports as well. For example, the Ultimate Fighting Championship (UFC), which follows USADA’s rules but not WADA’s, permits the use of cannabis except when an athlete intends to use it for performance enhancement. Under those rules, a case such as that of Richardson, in which the substance was used to deal with grief, would not have led to a ban, says Matthew Fedoruk, chief science officer of USADA.

Rather than relying on the results of a urine test alone—which is what was used to disqualify Richardson—the UFC requires additional evidence, such as behavioral signs of being under the influence, on the day of the fight. Fedoruk notes that because of the chemical properties of tetrahydrocannabinol (THC), it may appear in urine above threshold levels on the day of a test, making it an unreliable marker of in-competition use.

“We have advocated, and will continue to advocate, for changes in how marijuana is treated by the WADA rules to ensure they are fit for purpose in that they do not unnecessarily punish legal, out-of-competition use,” he says.

James Fitzgerald, a senior media relations and communications manager at WADA, notes that the organization’s list of prohibited substances is reviewed annually with input from scientific, medical and antidoping experts and stakeholders around the world “to ensure it reflects current medical and scientific evidence and doping practice.” The decision to remove a substance “is not based on one single piece of research or study,” he says.

But Ogle says that the research to date on issues such as cannabis’s effect on athletic performance is limited—leaving little evidence that authorities such as WADA can use to make these decisions. Although more studies are necessary, the legal status of marijuana makes this work a challenge. Even in the U.S., where many states have legalized marijuana, it is still a Schedule I drug—a category designated for substances with no accepted medical use and high abuse potential. “More research is needed,” Ogle says. “And in order to do that research, we need cannabis to not be Schedule I.”