Scholarly sources

The Effects of Home Video Game Violence and Fantasy Portrayals upon Enjoyment and Emotional State: A Gender Comparison
http://www.psu.edu/dept/medialab/research/ vgviolence.html
Violent video games attract more male than female players. The student shooters in Littleton, Colorado were both Doom players and both male. Video games have been criticized as the source of violence since this incident. The study proved that males are more apt to play in arcades, on computers and video games. The more violent the game, the better.

Study Finds Significant Amounts of Violence in Video Games Rated as Suitable for All Ages: Press Release
http://www.hsph.harvard.edu/press/releases/ press7312001b.html
In a study conducted by Kimberly Thompson, Assistant Professor of Risk Analysis and Decision Science at the Harvard School of Public Health, nearly 66% of a sample of E-Rated games had intended violence, and nearly 60% of those required violence to advance. It was recommended that members of ESRB (video game rating board) actually play the games that they rate instead of using summaries provided by the maker.

Some video games contain more violence than parents expect
http://www.researchmatters.harvard.edu/ story.php?article_id=273
This is a different article concerning the same study in the previous press release. The categories in the study were action, sports, role-playing, racing, puzzle, casino, and shooting. Violence was described as intended acts to hurt or kill somebody. It would be helpful if the ESRB standardize the content descriptors so that all video games and makers are categorized uniformly.

Video Games: Violence and Broken Bones
http://healthlink.mcw.edu/article/990318011.html
A study basis the return of rickets to video games due to the fact that long periods of time in front of a screen means less time outside in the sun. The sunlight helps supplement vitamin D. College students that played violent video games were more aggressive and not interested in academics.

Effects of Violent Video Games on Aggressive Behavior, Aggressive Cognition, Aggressive Affect, Physiological Arousal, and Prosocial Behavior: by Craig A. Anderson and Brad J. Bushman
http://www.psychology.iastate.edu/faculty/caa/abstracts/2000-2004/01AB.html
During a Commerce Committee hearing, researchers testified that there were valid reasons to be concerned about violent video games. High school students reported that 90% have parents that do not check the rating on a game before purchasing, and only 1% had refused to buy a game because of the rating. It was concluded that video-game violence increases aggression.

Violent Video Games and Aggressive Thoughts, Feelings, and Behavior: by Craig A. Anderson
http://www.psychology.iastate.edu/faculty/caa/abstracts/2000-2004/02A.jcc.html
A history of violence in video games and summary of studies that conclude that exposure to these games increase aggression. The discussion focuses on methodological issues, the potential of cumulative effects of repeated exposure, and on new research directions.

Violent video games and hostile expectations: A test of the general aggression model: by Brad J. Bushman and Craig A. Andreson (PDF download)
http://www.psychology.iastate.edu/faculty/caa/abstracts/2000-2004/02BApspb.pdf
This study assumes for a fact that exposure to violent video games causes violent behavior and moves on to ask WHY exposure results in this. The eight page study explains the "general aggression model" and proceeds to test it.

What Goes In Must Come Out: Children's Media Violence Consumption at Home and Aggressive Behaviors at School: by Audrey M. Buchanan, et al
http://www.mediafamily.org/research/report_issbd_2002.shtml
In a study by Bringam Young University and the National Institute on Media and the Family, the authors expand upon previous research on the issue of the effects of violent video games by examining subtypes of aggression in relation to media exposure (physical aggression and relational aggression).