The research found that children who exceeded the two hours per day of screen time were 1.5 to 2 times more likely to be above average in attention problems.
"There isn't an exact number of hours when screen time contributes to attention problems, but the AAP recommendation of no more than two hours a day provides a good reference point," said Edward Swing of Iowa State University (ISU).
"Most children are way above that. In our sample, children's total average time with television and video games is 4.26 hours per day, which is actually low compared to the national average," he added.
The researchers assessed 1,323 children in third, fourth and fifth grades over 13 months, using reports from the parents and children about their video game and television habits, as well as teacher reports of attention problems.
Another group of 210 college students provided self-reports of television habits, video game exposure and attention problems.
Douglas Gentile of ISU said that the pace of television programming might also have some brain-changing effects when it comes to attention span.
"If we train the brain to require constant stimulation and constant flickering lights, changes in sound and camera angle, or immediate feedback, such as video games can provide, then when the child lands in the classroom where the teacher doesn't have a million-dollar-per-episode budget, it may be hard to get children to sustain their attention" he said.
The researchers have also said that TV and video game viewing may be one contributing factor for attention deficit hyperactivity disorder (ADHD) in children.
"We know that the brain adapts and changes based on the environmental stimuli to which it is exposed repeatedly.
Therefore, it is not unreasonable to believe that environmental stimuli can increase the risk for a medical condition like ADHD in the same way that environmental stimuli, like cigarettes, can increase the risk for cancer," Gentile said.
Swing points out that the associations between attention problems and TV and video game exposure are significant, but small.
"It is important to note that television or video game time cannot solely explain the development of attention problems," he said. "Clearly other factors are involved."
Their study was published in Paediatrics-the journal of the American Academy of Paediatrics.