Some child psychologists argue that if young people see violence in films and television or play violent computer games they are more likely to become violent themselves.
One American study, started in the 1980s, found that children who watched large amounts of violence on television from the age of eight, tended to show higher levels of aggressive behaviour at the age of eighteen. They were more likely to be prosecuted for criminal acts as adults.
Other research has suggested that people who are likely to be aggressive are more likely to be drawn to violent media, rather than the media making them aggressive.
There has been less research into the effects of violence in gaming. A study from 2010 concluded that exposure to violent video games is a causal risk factor for increased aggressive behaviour.
Another study from 2009 agreed but found that increased aggression measured in the laboratory did not have a meaningful effect in the real world.
In 2010, an Australian government review of research into gaming found that:
In 2011 the Swedish Media Council carried out a review of over 100 articles about violent video games. It concluded that there is a clear, statistically significant link between violent games and aggressive behaviour but that there is no evidence that violent computer games cause aggressive behaviour.
It suggested that underlying factors like poor health and family problems could explain the violent behaviour and also may lead to a greater tendency toward playing violent games.