Researchers say roughly three out of five video games rated suitable for children as young as six years old reward players for injuring or killing characters.
"Physicians and parents should understand that popular E-rated video games may be a source of exposure to violence that rewards (children) for violent actions," said the report published in this week's issue of the Journal of the American Medical Association.
An E-rating is the video game world's equivalent of a G-rated movie, having "content suitable for persons aged 6 and older," said the report from the Harvard School of Public Health.
After compiling a list of 672 E-rated games, researchers at the Harvard Centre for Risk Analysis played 55 of them and then analysed videotape recordings of their play to assess the amount of violence in each game.
They found 35 of the 55 sampled E-rated games depicted intentional acts of violence ranging from 1.5 percent of the time in a hockey game to 91 percent of the time in an action game. Twenty-seven of the games depicted deaths from violence.
"Action and shooting games led to the largest numbers of deaths from violent acts, and we found a significant correlation between the proportion of violent game play and the number of deaths per minute of play," the report said.
The researchers called for more consistent ratings and content descriptions to educate parents about the nature of violent content in video games.
