Video Game Violence

How are you to objectively measure the effect of video games on level of violence?

Here are some articles about a study that tries to create an objective measure.

Techdirt: does-being-more-vocal-video-game-violence-debate-mean-you-have-better-argument.shtml
eurekalert: Press Release

So the way the "study" creates this objective measure is by weighing the number of publications produced by both sides of an argument. I wonder if they have ever heard of the field called publication bias.

Here is another study that finds a link between video games and mental health issues
Slashdot Article