Teenagers who play violent video games over a number of years become more aggressive towards other people as a result, 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 team at Brock University in Canada said their results were ‘concerning’ and wrote that violent games could ‘reinforce the notion that aggression is an effective and appropriate way to deal with conflict and anger’.
Evidence 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 findings come after a coroner urged parents to stop children using adult video games following the death of Callum Green, 14, from Stockport, who hanged himself after playing the Certificate 18 game Call of Duty, which features gruesomely realistic scenes of soldiers trying to kill each other.
Anders Breivik, the Norwegian who killed 77 people, claimed earlier this year that he had played Call of Duty to train himself for his ‘bloody and horrendous’ operation.
The study, published in the journal Developmental Psychology, 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.
Others who regularly played non-violent games did not show any evidence of increased aggression.
The trend remained even after taking into account other variables that could be linked to aggression such as gender, parental divorce and marijuana use.
Importantly, the study found no evidence that teens who were more aggressive to begin with were simply more likely to play violent games.
Pupils with high aggression scores in Grade 10 were not more likely to play violent games in Grade 11. But those who played violent games regularly in Grade 11 were rated as more aggressive the next year.
Lead researcher Professor Teena Willoughby said: ‘The current study is the first to demonstrate a relation between sustained violent video game play and the progression of aggressive behaviour.
‘It is clear that there is a long-term association between violent video games and aggression. This is an important and concerning finding, particularly in light of the hours that youth spend playing these games.’
Professor Mark Griffiths, director of the International Gaming Research Unit at Nottingham Trent University, said: ‘The study as a whole does provide one of the strongest pieces of empirical evidence to date that there is a direct relationship between playing violent video games and subsequent aggressive behaviour.’
Prof Willoughby said further research could look at whether the effect is solely due to violent content or whether fast-paced action and competition may also play a part.