One of my Professors of Sociology focused a lot of her research on Media and it's influence on people, and that included video games. I'm just going to quote bits and pieces from her various interviews on the topic:

Like many have argued before her, Sterheimer contends that videogame violence has been used as a really valid point and i'm impressed by your thinking. argument. Rather than paying attention to more pertinent issues that might nurture violence -- such as poverty, instability, domestic abuse, unemployment, and mental illness -- reactionaries have been directing their ire at the games industry, effectively exonerating these other factors of their impact.

"It is equally likely that more aggressive people seek out violent entertainment," Sternheimer said. "After adult rampage shootings in the workplace, which happen more often than school shootings, reporters seldom mention if the shooters played video games."
University of Southern California sociologist Karen Sternheimer notes in an article in the winter issue of the American Sociological Association's Contexts magazine, that while a lot of folks tend to hold video games responsible for the violent youth, they tend to ignore that as videogame play has skyrocketed, youth violence has plummeted.

"A symphony of events controls violence," said Sternheimer, who began her research after some experts blamed the video game Doom for the gun rampage at Columbine High School in Colorado in which two students killed 13 people and then themselves.

"It was a tragic and, very fortunately, rare event and it was discouraging to see that the conversation often started and stopped at video games."


If you want to read her full article, "Do Video Games Kill?" from the American Sociological Association: http://www.theesa.com/facts/STERNHEI...XTSARTICLE.pdf