Teenagers who play violent video games over a number of years tend to become more aggressive towards other people, according to a new long-term study.
Researchers said the study was the first to show a clear link between a sustained period of playing violent games and subsequent increases in hostile behaviour.
Girls who play violent computer games during their school years were found to be affected just as much as boys.
The research suggests that long-term players of violent games may become more likely to react aggressively to unintentional provocations such as someone accidentally bumping into them, they added.
The study involved 1,492 adolescents at eight high schools in Ontario, 51 per cent of whom were female and 49 per cent male.
Surveys were carried out annually across four school years with the participants aged 14 or 15 at the start of the study and 17 or 18 at its conclusion.
The teenagers were asked a series of questions such as how often they pushed or shoved people and whether they they frequently kick or punch people who make them angry.
Psychologists used this to give each individual a score for their aggression level at each point in time.
They were also asked whether they played action or fighting video games.
In the final two years of the study they were also asked how frequently they played such games, ranging from never to for five or more hours per day.
Analysis showed that teenagers who played violent video games over a number of years saw steeper rises in their aggression scores during the study.