Maybe, if you have difficulty differenciating between a fantasy game and reality.
To prove my point, there was a study here in Australia into the topic. They took a collection of young males in the age groups typical to those that play such games, and told them that, every time they killed someone, the person they killed would be punished in some way. The results of the study seemingly proved an increase in violent behaviour, HOWEVER, after the study was released, the people who took part in that study released a statement saying that the reason they were "violent" was that the whole setup was terrible, causing frustration ingame.
In my opinion, games such as this do not cause violence. In these types of games, you shoot someone in the head, their head will explode in a very violent and gorey fashion. In my opinion (and this will sound really stupid, but bear with me), it is shows like Looney Tunes and Power Rangers, the shows that most boys watch when they're young, that cause violence. Why? Because, when you think about these shows, how much senseless violence is there? In shows like Looney Tunes, people and creatures wield butcher's knives, cannons, bombs etc. They use them without thought. What happens to these characters?
Nothing. Absolute jack sh*t. They will turn black for a while, then go back to normal when they go to try their next plot. At least in these games, they show the conceuences. You shoot someone, they die. In these shows, which parents encourage their children to watch (at times), the consequences are not shown.
