Cause, no. Contribute? Yes.
At the bare minimum, the frequent, repeated acts of violence in videogames have a desensitization effect, which leads to a reduction in our ability to feel empathy and which makes us more tolerant of images of extreme violence. That said, the effect is, as far as I am concerned, not significantly more pronounced that that of any other form of visual media.
There's evidence to suggest that there is some increase in aggression in people, particularly kids, after playing violent videogames, but there's also evidence to suggest that that influence is easily countered.
AT WORST, videogames serve as a model for already violent or unstable people to base their violence on, and as a reinforcer of aggressive tendencies. No normal person is going to be made to commit an act of criminal violence as a direct result of playing videogames.
-m