It's a stretch to say a flat-out "no", because there is some evidence that violent games can cause a short-term raise in aggression in young people, or at least some young people. "Family" groups often seize on these findings as proof that violent games cause violent behaviour, but it doesn't really show that. What has never been proved is that violent video games can have lasting effects on someone's personality. Compare it to reading an action thriller novel: it might get your heart pumping a little faster and make you a bit wild-eyed for a few minutes after you put it down (which is what has been tested in the studies), but it probably doesn't make you more likely to punch someone in the face a week from now (what the conservatives say is proven).