A new meta-analysis of 130 research reports on more than 130,000 subjects worldwide 'proves conclusively' that exposure to violent video games makes more aggressive, less caring kids, say researchers from Iowa State University and the City University of New York.

The team used meta-analytic procedures -- the statistical methods used to analyze and combine results from previous, related literature -- to test the effects of violent video game play on the behaviors, thoughts and feelings of the individuals, ranging from elementary school-aged children to college undergraduates. The research also included new longitudinal data which provided further confirmation that playing violent video games is a causal risk factor for long-term harmful outcomes.

The analysis, published in Psychological Bulletin, found that violent video game effects are significant in both Eastern and Western cultures, in males and females, and in all age groups. Although there are good theoretical reasons to expect the long-term harmful effects to be higher in younger, pre-teen youths, there was only weak evidence of such age effects.

"These are not huge effects -- not on the order of joining a gang vs. not joining a gang," said Said Iowa State Psychologist Craig Anderson. "But these effects are also not trivial in size. It is one risk factor for future aggression and other sort of negative outcomes. And it's a risk factor that's easy for an individual parent to deal with -- at least, easier than changing most other known risk factors for aggression and violence, such as poverty or one's genetic structure."

The study has important implications for public policy debates, including development and testing of potential intervention strategies designed to reduce the harmful effects of playing violent video games, the authors say.

"From a public policy standpoint, it's time to get off the question of, 'Are there real and serious effects?' That's been answered and answered repeatedly," . "It's now time to move on to a more constructive question like, 'How do we make it easier for parents -- within the limits of culture, society and law -- to provide a healthier childhood for their kids?'"