Violent video games such as Grand Theft Auto may lead to greater thrill-seeking and risky behaviour among teenagers, a study has found.
Previous research has already linked the adrenalin-pumping interactive games with higher levels of adolescent aggressiveness.
The new findings show that teenagers who play the games are also more likely to engage in what are described as "deviant behaviours", including excessive drinking, smoking, stealing, fighting, and unsafe sex.
Whether video games cause such behaviour or whether "bad seed" teenagers with a latent propensity for rebelliousness and risk-taking are more likely to play the games is unclear.
But the research showed increases in deviancy over four years that were not seen in teenagers who did not play violent video games.
Professor James Sargent, from Dartmouth College in Hanover, US, who co-led the research published in the Journal of Personality and Social Psychology, said: "Up to now, studies of video games have focused primarily on their effects on aggression and violent behaviours.
"This study is important because it is the first to suggest that possible effects of violent video games go well beyond violence to apply to substance use, risky driving and risk-taking sexual behaviour."
The scientists recruited more than 5,000 US teenagers and conducted surveys of their use of video games from around the age of 14.
They focused on "mature-rated risk-glorifying" (MRRG) games, including Grand Theft Auto, Manhunt and Spiderman, many of which feature anti-social protagonists.
Playing the violent games was associated with subsequent increases in a wide range of high-risk behaviours.
Game players became more rebellious and thrill-seeking, partly because of changes in their personality, attitudes and values, said the researchers.
Similar effects were seen in boys and girls, and were strongest among the keenest player - especially when the games involved anti-social protagonists.
The authors pointed out that the primary character in Grand Theft Auto III was an "underworld thug" working his way up the criminal hierarchy. Spiderman's central character, on the other hand, was a superhero using his powers to fight villains.
The researchers concluded: "The current findings support the hypothesis that play of mature-rated, risk-glorifying video games can alter self-perceptions of personal characteristics, attitudes and values with broad consequences for deviant behaviour, including alcohol consumption, smoking, aggression, delinquency, and risky sex.
"Character-based video games provide an opportunity to practice being someone else. As a result, the behavioural consequences of playing such games are potentially much broader than the specific kinds of behaviours enacted in the game.
"With respect to playing deviant video game characters, we feel it best to follow the admonition in Kurt Vonnegut in Mother Night: We are what we pretend to be, so we must be careful about what we pretend to be."