From the American Academy of Family Physicians:
"The authors note that rates of adolescent violence, homicide, weapon-carrying, and other markers of antisocial behavior fell consistently during the period when violent video games became ubiquitous, more graphic, and more realistic. Furthermore, no consistent theories have emerged to explain a causative relationship between violent video games and antisocial behavior. Theories linking video games to violent behavior include learning and imitating aggressive behavior, arousal by the success or peer status of winning a violent game, and "priming" (changing the threshold at which violence seems acceptable or increasing the likelihood that ambiguous behavior is perceived to be threatening).
An extensive search of literature databases, personal contacts, and other sources identified 29 studies of this topic. The studies varied greatly in design and quality, leading the authors to conclude that a major deficiency in randomized, well-controlled studies prevents firm determinations from being reached. In children of middle-school age and younger, no association was found between video games and aggression in girls. In boys, studies report both increased and decreased aggression. Studies of middle- and high-school students predominately studied boys and often used self-report. Again, both calming and arousal effects were reported, and no consistent relationship was demonstrated between violent games and actual behavior. In college students and young adults, results were again mixed, but studies reporting calming effects were more common, particularly if the prior mood was hostile, angry, or aggressive.
The authors conclude that, contrary to popular impressions, little evidence supports concerns that violent video games are linked to aggressive or antisocial behavior. They caution that this topic is quite complex and not easily studied. The effect may depend on individual characteristics, including age and mood before playing the game, as well as the characteristics and complexity of the game itself. Modern, more realistic games may have very different effects than earlier versions. The authors do not regard violent video games as a significant public health concern."
From Science Daily:
According to Williams, researchers have suspected a strong linkage between games and aggression “but, with the exception of relatively short-term effects on young adults and children, they have yet to demonstrate this link.”
Williams and Skoric undertook the first longitudinal study of a game to see whether they could determine a link.
Because most video game research has been conducted in the laboratory or by observation in the field – methods “not representing the social context of game play” – they had their participants play the game in normal environments, like home.
The results of the new study, Williams said, support the contention of those who suggest that some violent games do not necessarily lead to increased real-world aggression.
Bottom line: A long-term correlation has never been found between video game violence and an increase in violent behavior. Children who play video games for an inordinate amount of time have a statistically-higher rate of delinquency and are more likely to drop out of high school, but I think anyone else who knows people who shoot their lives away in front of a TV screen could predict this for themselves.
Short-term brain effects are out-of-context at best and not statistically valid at worst, as the same brain effects have been observed in people playing competitive sports, listening to music or even watching a symphony.
Until researchers take these factors into account and value the scientific method rather than merely forwarding an agenda I am not obliged to entertain their baiting.