The announcement is perhaps the clearest sign yet that e-sports, as professional gaming is widely known, is evolving into a mainstream form of competitive entertainment. This year, overall revenue from the global e-sports business is expected to surpass $US250 million from more than 113 million e-sports fans worldwide, according to estimates from Newzoo, a games research firm. But the growing stakes for players — prize money is expected to reach $71 million — is creating new temptations. "We want to create a level playing field for all competitors and maintain the integrity of the sport," said James Lampkin, vice president of professional gaming at ESL. ESL has long had a general prohibition against doping, but its rules did not specify which drugs were not allowed, and the league did not police players. That changed, though, when Friesen, who plays under the name Semphis, was interviewed earlier this month and said that he had used Adderall during an ESL tournament for the shooter game Counter-Strike while playing with a team called Cloud9. In the interview, which was posted on YouTube, Friesen said that his teammates also used the drug, which is prescribed to people with attention deficit hyperactivity disorder but is commonly abused by some to help with focusing.

"We were all on Adderall," Friesen said of his team, which he no longer plays for. "Tons of people do it." Friesen, 26, said that he used Adderall out of desperation. His team was in the midst of a losing spell, so he turned to chemical help. "It was kind of when we were doing worse, so it was just one of those things where it's like, maybe it would help," he said in a phone call from his home in Abbotsford, British Columbia. It did not help. E-sports competitions look a bit like a trading floor, with players yelling directions to their teammates on where to go and who to ambush while simultaneously focusing on their own controllers and screens. Friesen said concentration drugs could probably help with the shooting bits, while making it harder to absorb directions. 'You don't just take Adderall and instantly become better," he said.

As for the response, Friesen said he wanted and expected a reaction from the leagues. "I didn't think it was good, whether that's hypocritical or not," he said. "I just think there should be some sort of rules that aren't supervague. Caffeine is technically a performance enhancing drug, but that wasn't banned." Jack Etienne, Cloud9's owner, said: "We don't agree with Kory's statements about Cloud9, and don't condone the use of Adderall unless it was prescribed for medical reasons. The team is willing to submit themselves to drug tests prior to events if event organisers offer them." As part of its new anti-doping effort, ESL said it would partner with the National Anti-Doping Agency of Germany to help develop a new policy. The league said it would also meet with the World Anti-Doping Agency about enforcing the policy. Lampkin said ESL would explore with the anti-doping agencies how well current testing methods detect drug use. He said that the whole industry may have to switch from online competitions, with players scattered across the globe, to predominately live, in-person games.

Traditional sports and e-sports have a similar motivation for curbing the use of performance-enhancing drugs: legitimacy. Traditional sports leagues, like Major League Baseball, worry that performance-enhancing drugs can raise doubts about a level playing field. What value is there in sacred home-run records, for example, if modern baseball players can get a big boost of strength from a drug? E-sports leagues and advocates, meanwhile, crave acceptance as a mainstream sport. By turning to some of the top anti-doping agencies, the leagues take a step closer to acting like a traditional sports league — adding to their sellout crowds and million-dollar paydays. "The more e-sports grows, the more it is going to be sanctioned by a governing body, and it was only a matter of before this was part of it," said Hector Rodriguez, owner of OpTic Gaming, a professional team. "We're becoming an actual sport, so that's why I welcome it." Although competitive gaming has been around for more than a decade, it has emerged as a serious business in the last few years. Game publishers and independent leagues like ESL and Major League Gaming have invested heavily in producing polished live events that can attract tens of thousands of spectators. Video streaming services like Twitch have been critical for bringing tournaments to millions more viewers online and creating conduits for players to interact with fans. Big corporate sponsors are also beginning to cater to e-sports fans.

Energy drink makers, in particular, have turned to marketing their products for gamers, suggesting that the caffeine- and sugar-filled beverages can improve play. Bruce Dugan, a spokesman for Major League Gaming, said that the organisation's policies prohibit the use of performance-enhancing drugs. "Now that a lot of attention is being paid, it's something we'll look at for the 2016 season," he said. The New York Times Follow Digital Life on Twitter