An analysis of 20 years of research in US shows the effects can be both immediate and long-lasting.

     "The majority of the studies would suggest there are effects," said Jessica Nicoll of Saint Leo University in Saint Leo, Florida, who worked on the study.

     One study showed that children who played a violent game for less than 10 minutes and then took a mood assessment test rated themselves with aggressive traits and aggressive actions shortly after playing.

     Teachers of 600 8th and 9th graders, aged 13 to 15, said children who spent more time playing violent video games were more hostile than other children and more likely to argue with authority figures and other students.

     The findings, presented at an annual meeting of American Psychological Association, prompted the group to adopt a resolution recommending that all violence be reduced in video games and interactive media marketed to children and youth.

     "Additionally, the APA also encourages parents, educators and health care providers to help youth make more informed choices about which games to play," the association said in a statement.

     Bad example video games set a bad example and may be particularly influential because a player takes on the roles of heroes and villains, violent and otherwise, the APA said.

     Perpetrators of violence go unpunished 73 percent of the time in all violent scenes, the group said.

(IRIB)