Meanwhile, 1,500 strong players were contacted to ask about the prevalence of drug use in the game.
The main study, published in a leading journal, was carried out by researchers from several German universities and the University of Stockholm, who analysed more than 3,000 games played by 40 players.
mong its findings were that modafinil, a drug used for treatment of disorders such as narcolepsy, improved players’ performances by an average of 15 per cent.
Methylphenidate, more commonly known as the ADHD treatment ritalin, boosted performance by 13 per cent, and caffeine, which they also tested, by around 9 per cent.
he study was carried out by giving each player a series of neuropsychological tests and questionnaires, then asking them to play against computers running the chess-playing programme Fritz 12.
One surprising finding, the World Chess website reported
, was that the drugs made the subjects play slower, suggesting that rather than enhancing decision-making, drugs improved players’ ability to spend more time on a decision and perform more thorough calculations.
rug-testing exists to some extent in chess, but only at events such as the world championship.
Magnus Carlsen, the Norwegian world champion, and his Russian challenger, Sergey Karjakin, were tested during their title match last November
Fide, the world governing body, adopted a drug policy in 1999 after it became a member of the International Olympic Committee, because the IOC requires members to be a signatory to the World Anti-Doping Agency.
As they were already on the Wada banned list, ritalin and modafinil were automatically prohibited while caffeine use was restricted.
However, so far no one is known to have tested positive.
The game’s only brush with a doping scandal to date was a curious incident involving the top Ukrainian Grandmaster Vassily Ivanchuk
who refused to provide a urine sample at the Chess Olympiad in 2008.
The “scandal” ended up fizzling out when it emerged Ivanchuk, the current world rapid chess champion, had just been so annoyed at losing he fell out with the official.
Dr Klaus Lieb, a professor of psychiatry and psychotherapy at the University of Mainz, in Germany, said: “There is lots of data showing that a subject in a sleep-deficient state or exhausted people do profit from an enhancer.
“We recommend to introduce rigorous doping controls in chess competitions.”