Violent video games increase aggression.

[Mystic]

A new study suggests a dose-response relationship among playing violent video games and aggressive and hostile behavior, with negative effects accumulating over time.

Investigators discovered people who played a violent video game for three consecutive days showed increases in aggressive behavior and hostile expectations each day they played. They also found that those who played nonviolent games showed no meaningful changes in aggression or hostile expectations over that period.

http://psychcentral.com/news/2012/12/11/...48918.html