Considering that gun violence has been on the decline and mass shootings constitute roughly one percent of overall gun homicides, I think that the media coverage on mass shootings is overblown. Even so, there is a preponderance of questioning as to why these unfortunate shootings occur in the first place. One theory that has become popular, and has even garnered favor with the National Rifle Association, is that of video games causing increased violence. The premise is that the violent images in video games desensitize the gamer, thereby making the individual more prone to violence. Since video games are a way that people, and children in particular, interact with the world, there is certainly intuition to the video game violence theory.
Before we even delve into the studies, a brief word about the theory itself. In order to prove causality, you first need to have correlation. Without it, you can't say something like "video games cause an increase violence." For the more simplified version of the theory to work, an increase in video game purchases would lead to an increase in violence. However, as Max Fisher over at the Washington Post illustrates, there is no correlation between video games and violence when looking at the ten largest video game markets. This is not to say that it is not possible for video games to increase violent tendencies in certain individuals, but rather that on the aggregate, it does not seem to have an effect on overall violent crimes, especially since the rate of violent crimes has been decreasing since video games started becoming prevalent in the mid-1980s. The reason why it is difficult for the "video games causes violence" theory to work is because video game consumption has increased substantially while youth violence is at a forty-year low.
Going to the studies, the truth is that some studies show increased aggression (e.g., Greitemeyer and Mügger, 2013; Delisi et al., 2012) while others show no link between video games and violence (e.g., Parkes et al., 2013; Ferguson et al., 2011). Oxford just came out with a study (Przybylski et al., 2014) showing that if there is any aggression, it doesn't come from the violent nature of the games, but the frustration of being incapable to master the technology and the game itself. Also, back in 2011, even the Supreme Court thought the connection between video games and violence was spurious, which would explain its 7-2 ruling in Brown v. Entertainment Merchants Association. The Australian government came to similar conclusions to those of the Supreme Court. Millions of people play video games, but the vast, vast majority don't go out and kill others because "the video game gave me the idea." If anything, it can be used as an outlet for one's violent tendencies, or to put in economic terms, video games have a substitution effect for the real thing (Cunningham et al., 2011), which could potentially help explain the decrease in violent crimes (Gunter and Daly, 2012). After all, there is a difference between aggression and downright violence.
How does this affect how we approach video games in a public policy sense? One is that we have not addressed that video games also come with benefits (Granic et al., 2013). There are a good amount of consumption goods that come with risks, like alcohol, marijuana, or even sugar and trans-fats. At the very least, we should look at the benefits, as well as the costs, before rushing to a decision with regards to video game regulation. If you are going to even begin regulating video games in such a fashion, you better have a less specious reason for doing so. The second is that we have an issue with whether video games cause violence or whether it is merely a manifestation of children that are already violent, i.e., possibility of reverse causation. There is also the possibility that the video games are a reflection of the social milieu, and not a cause of it. Third, people come with free will. To reiterate, millions of people play video games containing violence, and they never go out and harm another living soul. Video games have not been even remotely shown to diminish one's free will, and we should not allow individuals to abscond from the consequences of their actions simply because they have played Call of Duty. We are responsible for cultivating our minds and how we interact with the world. Even when discussing children, it is prudent to point out that parenting should be in the hands of the parents, and that they have a more individualized understanding than a blanket prohibition or regulation that the government could provide. It's amazing what civic pressure and peaceful social interactions can accomplish. If we are going to go down this road of censorship, we might as well start banning comic books, the Internet, movies, certain music, or other literature, none of which is conducive to a free society. Fourth, if the relation is that causal, why don't we have a lot more murderers on the streets? Gaming has become so widespread that a causal link would be obvious by now. Fifth, the industry is self-regulated through game ratings through such organizations as the Entertainment Software Ratings Board. Finally, if we want to address violence, video games are a peculiar place to start. We should look at facets like mental health or even societal views on masculinity to help get at the root of gun violence instead of tenuous connections with little to no evidence.