According to the American Psychological Association, there's a link between violent video games and aggression.  The researchers concluded that there was no single risk factor to blame aggression but violent video games is a risk factor.  A taskforce was assigned to review hundreds of studies published from 2005 until 2013.  APA combined the results of these studies in order to look for patterns and correlations, rather than carrying out any new research itself.  This finding was immediately questioned by more than 200 academics.   

According to the report, "The research demonstrates a consistent relation between violent video game use and increases in aggressive behaviour, aggressive cognitions and aggressive affect, and decreases in pro-social behaviour, empathy and sensitivity to aggression".  It added, "It is the accumulation of risk factors that tends to lead to aggressive or violent behaviour. The research reviewed here demonstrates that violent video game use is one such risk factor."

However, according to Dr. Mark Coulson, associate professor of psychology at Middlesex University that there's no evidence linking crime and violence with violent video games, "I fully acknowledge that exposure to repeated violence may have short-term effects - you would be a fool to deny that - but the long-term consequences of crime and actual violent behaviour, there is just no evidence linking violent video games with that".

Playing violent video games has been cited as a factor in inspiring youth crimes such as the high school shootings in the United States.  However, the taskforce admitted that more research is needed to establish a concrete link between violent games and violent criminal behaviour. 

In an open letter to the APA submitted by 230 academics from around the world, they cited that that the violence in the U.S. and around the world was currently "at a 40-year low".  "This decline in societal violence is in conflict with claims that violent video games and interactive media are important public health concerns," they wrote.  "The statistical data are simply not bearing out this concern and should not be ignored."

Another study was just released by Oxford Internet Institute last year suggesting that frustration from not able to play video games are more likely to bring about aggression.  This is in contrast to the findings generated by APA.