The findings were released by Common Sense Media, a non-profit organization.
Study leaders said parents need to keep tabs on what their kids are exposed to and over how much time. They also called for more detailed research.
"There's no research on new digital media - cell phones, iPods, the Internet - and it's real impact on kids' health. So there needs to be a whole new set of research on that. Second, there oughta be media education and media literacy in every school in the United States," said James Steyer of Common Sense Media.
NIH researchers said the average child now spends 45 hours per week with electronic media.