Video Games and Violence Part II
"...the study published in the Journal of Youth and Adolescence, researchers found that the playing the video games actually had a very slight calming effect on youths with attention deficit symptoms — and helped to reduce aggressive and bullying behavior."
Link to work:
http://www.ncbi.nlm.nih.gov/pubmed/23975351
In a previous analysis by Ferguson, et al:
".... Results from both sets of analysis revealed that exposure to violent game had neither short-term nor long-term predictive influences on either positive or negative outcomes. A developmental analysis of the cross-sectional data revealed that results did not differ across age categories of older children, preadolescents or adolescents. Analysis of effect sizes largely ruled out Type II error as a possible explanation for null results. Suggestions for new directions in the field of video game research are proffered."
http://www.ncbi.nlm.nih.gov/pubmed/22875464
Me thinks that this research done spurred the latest work.