Sydney (dpa) - Australia's Okan Kaya likes Call of Duty: Black Ops II. In November he played the blockbuster video game for a world-record 122 hours.
"I'm a massive fan," he said. "I've been playing the series since the World War days and absolutely love it."
Circumstantial evidence suggests gaming can be as addictive as gambling. In July a Diablo III fan in Taiwan collapsed and died after a 40-hour session at an internet cafe.
Australian National University psychologist Olivia Metcalf has found concrete evidence that gaming is indeed addictive.
For her research, which showed that addicted gamers had trouble focusing on other tasks, she gathered volunteers representing: those who were addicted; those who were regular players but who were not addicted; and a control group of non-players. They were tested for their responses to gaming-related words.
"We found that the attention system of an excessive gamer gives top priority to gaming information," she said. "Even if they don't want to think about gaming, they're unable to stop themselves."
She said that the phenomenon, known as attentional bias, is common among heroin, tobacco, alcohol and gambling addicts and is thought to be a factor in developing an addiction.
"Each type of addictive substance or behaviour has unique risks associated with them," she said. "The unique aspect of excessive gaming is the sheer amount of time that can be spent playing video games."
Does spending a very long time gaming make you an addict?
No, she said: "The majority of gamers enjoy games without any consequences, even if they are spending some days playing for long periods."
So world champion Okan Kaya can rest easy: addiction to gaming is not a product of too long at the screen.
"It's not something that occurs because you do a behaviour a lot," Metcalf said. "It's some sort of change that occurs in your attention system, in your brain, when an addiction is developing."