Video games have been violent since their inception. Space Invaders, for example, had you shooting aliens to pieces before they destroyed your base. Super Mario Bros. had you squashing poor Goombas under your feet. And Grand Theft Auto allows you to beat up just about every person you see in its virtual streets.That violence has always been linked, but never proven, to causing violent behavior. But now, a new study shows how violent video games may contribute to increased aggression and a decreased sensitivity to it.

On Thursday, the American Psychological Association (APA) announced the release of a 49-page report from its Task Force on Violent Media, which was founded in 2013 to look at the scientific literature published between 2005 and 2013 that investigated the effects of violent video games. The report found that although violent video games may increase aggression and desensitize people to it, there is insufficient evidence to determine whether violent games also lead to criminal violence or delinquency.

"The research demonstrates a consistent relation between violent video game use and increases in aggressive behavior, aggressive cognitions, and aggressive affect, and decreases in prosocial behavior, empathy, and sensitivity to aggression," the report concluded. It goes on to state that “no single risk factor consistently leads a person to act aggressively or violently. Rather, it is the accumulation of risk factors that tends to lead to aggressive or violent behavior.”

As a result, the APA will adopt new policies and recommendations — first by replacing its 2005 study, "Resolution on Violence in Video Games and Interactive Media." The new document will be called, “Resolution on Violent Video Games.” In it, the APA will encourage the Entertainment Software Rating Board (ESRB) to refine its video game rating system “to reflect the levels and characteristics of violence in games, in addition to the current global ratings.”

Despite these actions, researchers said the study results weren’t conclusive and that further research will be necessary. This research would differentiate between males and females who play games, the effects of violent video games on children under 10, and the effects of a game’s violence over the course of a child’s development.

There will most likely always be violence in video games, as they continue to be popular. Grand Theft Auto V has sold more than 54 million copies since 2013, Space Invaders found its way into the Pixels movie, and Super Mario Bros.’ protagonist, Mario, is a global icon. While there may be no stopping the proliferation of these games, reviews like the APA’s will help people better understand violence in games and who should be playing them.