In two national surveys of children aged 12 to 15 years, researchers at the U.S. Centers for Disease Control and Prevention found that nearly three-quarters spent at least two hours a day watching TV and using a computer.
The surveys also found that 15 percent of teens watch four or more hours of TV daily, while nearly 12 percent report using their computers for four or more hours a day. The surveys didn't ask teens about their use of smartphones. The findings are published in the July issue of the NCHS Data Brief.
"The findings are concerning, but not surprising," said Dr. Marjorie Hogan, a pediatrician who helped write the American Academy of Pediatrics (AAP) guidelines on kids' screen time.
The AAP has long recommended that children and teens devote no more than two hours to entertainment media each day. That advice is based on research linking more screen time to obesity, higher blood pressure and cholesterol, sleep loss and problems at school.
This latest CDC study found that teenagers' weight did, in fact, correlate with their screen time: Only 20 percent of obese kids were limiting TV and computers to two hours per day -- versus 31 percent of their normal-weight peers.
Hogan said parents have a tough task limiting TV and computers for kids in that 12 to 15 age range -- especially in the age of social media.
"That's why it's so important for parents to begin discussions about media use at an early age," Hogan said.
She added that the AAP recommendations are not intended to "bash" TV or the Internet. Instead, she said, media consumption can be seen the same way as food consumption.
"I like the concept of the 'healthy media diet,'" Hogan said. "It's all about moderation and choosing wisely."
Dr. Angela Diaz, director of the Mount Sinai Adolescent Health Center in New York City, agreed that parents should start the moderation message early.
"It's important to try to establish children's habits early in life," Diaz said. "Try to create an environment where kids have choices other than TV and computers."
That, she said, includes getting children involved in after-school activities, whether sports, dance, music or art. For older kids, Diaz noted, volunteer work is a good choice, too -- because they'll be interacting with, and helping, other people.
Diaz said, even though a lot of the concern with excessive screen time is that it makes kids couch potatoes -- which could affect their physical health -- there is also an important social aspect.
Teens may think they're being social online, but that can't take the place of face-to-face relationships, Diaz stressed.
"It's important for kids to be connected to people," she said, "and not just isolated in their own rooms."
Hogan agreed. "Social-media tools are great. We all use them," she said. "But you also have to get out there and talk to people."
That advice goes for adults, too. "Parents have to be role models," Diaz said. Families need to sit down together for meals and have conversations, she said -- which means turning off the TV and ignoring the phones and other devices they use all day.
Hogan said parents should also ban TVs and computers from their kids' bedrooms. That's, in part, so they can monitor what kids are doing online. But it's also to ensure that screen time is not getting in the way of sleep time.
"Research is showing that screen use at night really disrupts sleep," Hogan said. "And it is absolutely key that kids, including teenagers, get enough sleep."
The American Academy of Pediatrics has tips on family media use.