Low-income boys seemed to benefit the most from the change in programming, the researchers found.
"The point is, this is something that is as effective as other things we do to try to modify behavior in children, and it's fairly simple," Christakis said.
Christopher Ferguson, a psychologist from Texas A&M International University in Laredo, said not all studies have shown violent programming leads to aggression and behavioral problems in children, and the new study doesn't shut the door on that question.
"There's not much here for parents to take home," Ferguson, who wasn't involved in the research, told Reuters Health.
"Parents certainly should be aware of the media content that their kids are consuming, be informed, put some effort into playing video games with their child or watching the TV shows with their children, and make individual decisions that they think are right for themselves or right for their families," he said.
But, he added, they should also "be wary that there's going to be lots of other people telling them what to do."
The new findings were reported Monday in Pediatrics.
TV AND ANTISOCIAL PERSONALITY?
Another study published in Pediatrics found the more TV that kids and teens watched, the more likely they were to have a criminal conviction or be diagnosed with antisocial personality disorder by age 26.
Researchers led by Lindsay Robertson from the Dunedin School of Medicine in New Zealand said children may imitate or internalize violence they see - or more time in front of the TV could simply mean less interaction with peers and families, and worse performance in school.
However, it's unclear from that study whether the TV watching, itself, caused future problems.
The American Academy of Pediatrics recommends kids watch no more than one to two hours of high-quality programming each day.
Researchers agreed parents should be mindful of what exactly their young kids are watching on TV, as well.
"It's not just about turning the TV off, it's about changing the channel," Christakis said.