This article has done the rounds for a while
There hasn't been a study yet that has conclusively proved either way. The reason is because it depends on who is playing the game, not the content of the game, because some people are just nuts.
There's been a few instances where games have been the catalyst for a violent act, though these are nearly always caused by actions of other players in a game's environment.
These studies linking it with aggression? I would venture a guess and say that it does so to a far lesser extent than playing sport, where such aggression is encouraged. It's competition and it's human nature to compete aggressively.