NOVA is a research institute of the Norwegian Ministry of Education and Research. It has published a report that summarises and discusses the findings from research on the association between violence in the media (including video games) and personal violence in practice. The report reviews academic literature between 1995 until 2010, supplemented with contributions prior to 1995 which are of particular interest.
On the basis of the studies of this report NOVA does not find any reason to exercise extreme caution in giving advice or making recommendations.
A prudent conclusion would be that media violence can be injurious for some. The uncertainty associated with this is nevertheless so large that it is difficult to defend comprehensive and costly measures which would reduce media violence to a degree [...]. On this basis, we cannot base our relation to media violence on the extent to which it can be maintained that such violence is injurious. An evaluation of media violence should preferably be controlled by those values which society wishes to promote, and which ultimately cannot be measured empirically.
The full study can be downloaded on NOVA's website.