Boys aged 2 to 5 who viewed an hour of on-screen violence a day increased their chances of being overly aggressive later in childhood, but the association was not seen in girls, researchers said on Monday.
"This new study provides further evidence of how important and powerful television and media are as young children develop," study author Dr. Dimitri Christakis of Seattle Children's Hospital Research Institute said.
"Of 184 boys (in the study), 25 of them had serious problems with aggression and for each hour on average per day they had watched violent TV, they were three times more likely to be in that group" than those who did not watch violent programming, Christakis said in a telephone interview.
Christakis and fellow researchers, writing in the journal Pediatrics, analyzed the television and video viewing habits of 330 children aged 2 to 5, then assessed their behavior five years later.
Christakis said many parents may be unaware that the shows or video games their young children watch are violent or inappropriate for their age group...
The association between violent programming and overly aggressive behavior was not found among the 146 girls in the study, who tended to watch more educational and nonviolent shows than the boys, Christakis said.
Boys may be more genetically predisposed to aggression, "so the same level of exposure brings out aggression in them where it doesn't in girls. It also could be boys are socialized to respond aggressively," he said.