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Emerging Science on Cannabis/Marijuana: Implications for Student Athletes

Submitted by Jason R. Kilmer, Ph.D. University of Washington

When Washington and Colorado legalized marijuana for nonmedical/personal reasons (note: there’s been a strong push away from the term “recreational” marijuana, since that term evokes outdoor or physical activities, including campus rec centers, and we don’t refer to “recreational” alcohol use), it was clear that the research needed to “catch up” with what people were using. Now, as the end of 2019 approaches, the research is catching up and tells a pretty compelling story related to marijuana use and the health and well-being of student-athletes.

Marijuana potency in 2019 is different than in the past.

THC is the most well-studied cannabinoid in cannabis, and published research has documented increases in THC levels from 1.5% in the 1970s to 2-3% in the 1980s to 4% by 1995 (El Sohly, et al., 2016; Volkow, et al., 2014). Then, levels skyrocketed to over 8% by 2004 and over 10% by 2010. By 2016, the average THC potency in the United States exceeded 13%, while in Washington, the state’s second Marijuana Impact Report showed that THC levels were over 21%. When people say they used marijuana in the past and didn’t experience harms (i.e., saying, “It’s just weed”), the truth is they were using a very different substance, and it stopped being “just weed” years ago. This can have significant implications for college students today.

Marijuana use is associated with increased mental health risks.

A study released earlier this year (Di Forti, et al., 2019) showed that daily use of cannabis over 10% THC increases the likelihood of developing psychosis 4.8 to 5.8 times compared with those who do not use marijuana. Recall from above that the average THC potency in the United States is over 13%, and legal states tend to see potencies up to or more than double this level. When people get addicted to marijuana (and there are clear criteria for cannabis use disorder), withdrawal symptoms include, but are not limited to, depressed mood and anxiety. Fischer and colleagues (2017) warn that those with a predisposition for or first-degree family history of psychosis or substance use disorders should refrain from using marijuana outright. If students are struggling with anxiety, depression or other mental health issues, these can be exacerbated by marijuana use. Thus, getting students connected with support services can be a priority.

Marijuana use impairs athletic performance.

In 2013, Pesta and colleagues referred to marijuana as an ergolytic agent, or a substance that impairs exercise or athletic performance (different, of course, from ergogenic, or performance-enhancing, substances). Since that time, articles have certainly told a consistent story about impairing performance. Gillman and colleagues (2015) showed that marijuana use decreased physiological work capacity and reduced maximal exercise duration. Kennedy (2017) showed that marijuana use resulted in no improvement in aerobic performance (with some studies showing no impact and some studies showing that aerobic performance worsened), and Lisano and colleagues (2019) showed a trend for those using marijuana to demonstrate increased fatigue during anaerobic (or power) testing. The latter study led the researchers to conclude that in sports where power is important, coaches should encourage athletes to refrain from marijuana use. Ware and colleagues (2018) documented the impacts of cannabis use on elite athletes, warning of acute effects including memory impairment, decreased judgment and reduced coordination, and chronic effects including addiction and poor academic performance. Messaging from coaches has long been associated with decisions student-athletes make about substance use, so clear messages around nonuse of marijuana are indicated.

Marijuana use is associated with poorer academic outcomes.

Marijuana use slows neuronal activity in the hippocampus, which affects attention, concentration and memory. A full 24 hours after marijuana use, there are measurable decreases in these cognitive abilities, and the more heavily someone typically uses, the more pronounced these decreases are. It can take 28 days of abstinence after daily use to see these declines go away, meaning that a student struggling with memory or attention who is also reporting marijuana use will, in fact, see improvements in time when they stop, but it requires that extended time or break (Pope & Yurgelun-Todd, 1996, Pope et al., 2001, Hanson, et al., 2010). Other studies have shown that the more frequently students use marijuana, the lower their grade-point average is, the more classes they skip, and the longer it takes them to graduate (Arria, et al., 2013, Arria, et al., 2015, Suerken, et al., 2016). The good news? When people make changes in their marijuana use, they can see improvement in these academic outcomes (Meda, et al., 2018).

Clearly, in a changing legal climate, increasing student-athletes’ exposure to what the science says about marijuana use can be a focus of alcohol and other drug education and prevention efforts. Messaging from coaches and trainers is important. Understanding the impact on them as students is important. And if a student-athlete is seeking to manage pain, anxiety or depression, then consulting with trainers and other providers to get connected to services and treatment with demonstrated effectiveness is important.


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Arria, A.M., Caldeira, K.M., Bugbee, B.A., Vincent, K.B., O’Grady, K.E. (2015). The academic consequences of marijuana use during college. Psychology of Addictive Behaviors, 29, 564-575.

Di Forti, M., Quattrone, D., Freeman, T.P., Tripoli, G., Gayer-Anderson, C., Quigley, H., Rodriguez, V., et al., (2019). The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): A muticentre case-control study. Lancet Psychiatry, 6, 427-436.

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