Violent video games have already been linked to increased aggressiveness in teenagers. Now a new study has found that teens who play these types of games are also more likely to take part in risky behaviours, such as consuming alcohol, smoking and engaging in risky sex.

According to US researchers, mature-rated games that glorify risk - particularly character-based games with anti-social characters - seem to affect how teenagers think about themselves and this can have consequences for the real world.

"Up to now, studies of video games have focused primarily on their effects on aggression and violent behaviors. 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 behavior," commented the study's co-author, Prof James Sargent, of Dartmouth College in New Hampshire.

The study involved over 5,000 randomly selected teenagers who answered a series of questions over a four-year period. The researchers looked at the effects of playing three specific mature-rated, violent games - Grand Theft Auto, Spiderman and Manhunt, and compared them to the playing of other mature-rated games.

The violent games were found to increase the risk of high risk-behaviours, such as delinquency, smoking, drinking and risky sex. The researchers believe this is due in part to the players' attitudes, values and personality.

The results were similar in males and females, although the strongest results were seen in those who played the most, and those playing games that included anti-social characters.

Details of these findings are published in the Journal of Personality and Social Psychology.