Limiting children's time in front of the computer and TV can lead to more sleep, doing better in school, better behavior and other health benefits, a new study finds.The Iowa State University study was published in JAMA Pediatrics.Lead author and Associate Professor of Psychology Douglas Gentile said the effect is not immediate and that makes it difficult for parents to recognize.  He said it's important for parents to monitor the time their children spend in front of a screen."When parents are involved it has a powerful protective effect across a wide range of different areas that they probably never would have expected to see," Gentile said in a news release. "However, parents aren't likely to notice that putting limits on the children's media is having these effects seven months later."Researchers said most children average 40 hours per week in front of a screen, not counting time spent on a computer at school.  They said even small changes in screen time could make a big difference.Gentile said he was not surprised to see a direct impact on sleep, academics and behavior.The study looked at the habits of 1,300 school children."Even with changes that we do notice, we really don’t recognize in the moment how all these things are related to each other across time," Gentile said. "Yes, as screen time goes up, school performance goes down, but that doesn't happen overnight. If I watch a lot of TV today, I don't get an F in my class tomorrow."Look for more on this story later today on KCCI-TV, KCCI.com and on our mobile website and apps.