While being illegal in many jurisdictions, cannabis smoking has been claimed as being helpful for some activities such as extreme sports, as it may improve muscle relaxation, reduces anxiety, and help users overcome fear memories (e.g., negative experiences), potentially leading to enhanced performance [1]. For these reasons cannabis has been included on the World Anti-Doping Agency (WADA) list as a substance prohibited in-competition. In fact, there are only a few data regarding its effectiveness and previous reviews concluded that there is a lack of evidence regarding performance-enhancing effects [2,3]. Based on this lack of data and its negative effects on cognition, including impairment of decision making and alertness [1], as well as its status as illegal drug (where applicable), cannabis smoking is clearly not advisable for professional and amateur athletes alike. However, beside all these regulations and concerns regarding its effectiveness, the smoking of cannabis and consumption of supplements containing cannabinoids appears to be popular in public and elite sports.

The potential advantages of cannabis in sports have certainly stimulated interest surrounding cannabidiol (CBD), which is one of the cannabinoid compounds naturally found in Cannabis sativa. CBD is structurally related to the main psychoactive compound Δ⁹-tetrahydrocannabinol (THC), which is responsible for the adverse effects of cannabis. CBD is non-psychoactive, but some pre-clinical evidence points to the fact that it may be responsible for some of the advantageous effects of cannabis for sports activities, such as decreased anxiety and fear memory extinction [1]. The further advertised effects of CBD for athletes include anti-inflammatory properties, the relief of arthritis and pain-related behaviors, as well as post-exercise recovery [4]. Consumers’ interest in CBD has considerably increased since 2015 and is still accelerating [5].

According to the World Health Organization (WHO), CBD is an effective treatment of epilepsy, and there may be some preliminary evidence for its application in a number of other medical conditions. The WHO also remarked upon the unsanctioned use of CBD-based products available online for the treatment of many ailments [6]. While CBD is generally well tolerated with a good safety profile [6,7,8], THC-like subjective or physiological effects have been reported. However, these may be due to THC-contamination of CBD-products rather than due to the CBD itself [9]. Nonetheless, some recent animal experiments have raised concerns regarding the hepatotoxicity [10] and reproductive toxicity [11] (see review in [12]).

Cannabidiol is currently approved in the European Union (EU) in a single medicinal product, namely Epidiolex^® for the treatment of seizures in patients with two rare, severe forms of childhood-onset epilepsy. However, most of the CBD products worldwide are available as food supplements or compounded foods with CBD or hemp extract as an ingredient [13]. Such unapproved products, which normally do not comply with quality standards, are currently easily available to athletes. A survey of cannabis use patterns in the US detected that older athletes who are newer to cannabis tend to only use CBD. However, in these athletes it provided the least reported benefit (albeit, with the least adverse effects) [14].

The WADA has excluded CBD from its list of prohibited cannabinoids [15]. However, it is important to mention that, according to the 2020 prohibited list of the WADA [15], cannabinoids in general still are listed in group S8, as substances forbidden to be used in competition. Here it is defined that all naturally occurring and synthetic cannabinoids—except CBD—are forbidden. Because most CBD products are sold as so-called full-spectrum products, they also contain other cannabinoids. Therefore, in competition, the use of full-spectrum CBD products is definitely prohibited by WADA. Moreover, the WADA remarked that “athletes should be aware that some CBD products extracted from cannabis plants may also contain THC that could result in a positive test for a prohibited cannabinoid” [15]. The threshold for a positive THC test has been set by WADA to 150 ng/mL of 11-nor-9-carboxy-THC in urine [16]. Other organizations, such as Drug Free Sports International, similarly warned that contaminated CBD products may cause positive urine tests [17].

The possibility of positive drug testing following CBD oil use is certainly more than a hypothetical risk. Studies worldwide have detected residual levels of THC in CBD products [9,18,19,20,21]. Most recently our group has detected THC in dose levels of >2.5 mg/day in 10 out of 28 commercial CBD products from the German internet and retail market [9]. Positive urine drug testing for several days may be expected from daily oral doses of more than 1 mg [13,22]. Therefore, more than 1/3 of CBD products on the German market—if consumed by athletes—would probably lead to false-positive urine doping tests.

This commentary therefore wants to provide a warning against the negligent use of CBD in athletes and provide the following considerations for consumers.