Even infants are drawn to the boob tube with its bewitching, transfixing blend of moving images and sound. And despite decades of concern about the influence of television and recreational computer use on children—coupled with newer worries about childhood obesity—researchers are still parsing out how this ever-expanding amount of screen time is affecting their well-being.

Despite the worries, TV use among the youngest viewers has continued to increase over the years. U.S. kids aged two to 11 now watch more than 25 hours of (non-prerecorded) television a week, which boils down to an average of more than three and a half hours a day, according to a 2010 Nielsen report. The American Academy of Pediatrics, however, recommends no more than one to two hours of "quality programming" a day, listing "violent or aggressive behavior, substance use, sexual activity, obesity, poor body image and decreased school performance" as among possible ramifications of too much unguided TV viewing. And research from the past few years has shown that children who spend more downtime in front of a screen are more likely to have emotional, social, conduct and concentration problems.

Physical activity has been linked to both better physical and mental health in kids and teens, and, many people reason, could be an antidote to excessive TV time. But can exercise undo some of the electronic-linked ills?

A new study published online October 11 in Pediatrics examined TV and recreational computer use and physical activity levels in children aged 10 and 11. To measure activity level and sedentary time, the researchers assessed readings from accelerometers attached to the belts of 1,013 children in Bristol, England. Children, who "are more reliable than their parents," reported their own television and recreational computer time and took a psychological health survey to measure their mental well-being, explains Angie Page of the Center for Exercise, Nutrition and Health Sciences at the University of Bristol and a co-author on the new study.

Scientific American spoke with Page about whether plenty of physical activity seemed to balance out any poor psychological health among kids who had more than two hours of recreational screen time a day, and whether TV and computer time actually decreases mental health or is simply a likely indicator of it.

[An edited transcript of the interview follows.]

So how much recreational screen time did these 10- and 11-year-old kids have?

If you look at the two-hour-per-day group, about 66 percent, or two thirds, exceed that target.

Could you tell,  among those high users, if many were getting much more than two hours of screen time a day? And if so, whether that correlated with even worse psychological well-being?

This isn't in the paper, but it's quite a dose-response effect, and certainly the effect is more marked if you go in for more hours.

Many people probably think that if a child is getting enough exercise, the extra TV or computer time doesn't matter quite as much. Does that seem to be the case?

It's not unreasonable to assume that high levels of physical activity might compensate. But it's only above the two-hour threshold that you start to see the negative psychological effect of screen viewing.

Is it the actual screen time that correlates with poor psychological well-being in kids, or is it a sedentary lifestyle in general? If you're plopped down to read a book, you're also inherently not getting exercise.
In this paper it's the TV and computer use that's more strongly associated with negative well-being. There's lots of evidence that physical activity is good for mental health for children, but you can't rely on it to compensate for high levels of screen viewing. It helps, but it doesn't seem to help enough for high levels of screen viewing.

Being inactive isn't the problem—it's what you're doing in your inactive time. Essentially, it does seem to be something about the medium.

Why do you think the medium matters?

This is an association, and we are following up with these children, and we'll follow them into adolescence. There was no correlation between high amounts of time spent inactive and negative psychological health. It's not so much that you're not moving—it's that you're watching TV or playing a computer game. So it's the medium or media.

Does there seem to be much difference between boys and girls?
You generally don't see much of a gender difference at this age.

Do you think this correlation would likely hold true for adults, too?
It seems to be whether adults are moving or not. There are some suggestions in the literature that sedentary time, but not what you're doing, is more important—but it's not a consistent picture in the literature.

In your recent study you actually found that physical activity was not always associated with good psychological health. That seems surprising, given previous findings.
The dominant view is more activity in young people is associated with better mental health. But there are two other sides, which relate to hyperactivity and conduct problems: The more physical activity you do the better your emotional well-being, but the worse you do on these hyperactivity and conduct problems.

What's the likelihood that children who have underlying emotional or psychological troubles are just more likely to "plug in" to electronic media than those who are mentally healthier?
What we are doing now is following up on these children to determine whether it's one that comes before the other. At the moment, we don't know the direction—it could be either. We're following them up to sort out that directionality issue and to see what are the factors that influence the high screen viewing so we can start to think about how we might intervene. For instance, are parents more important or friends?

So is screen time in excess of two hours a day something that could be useful in the future to help flag underlying psychological problems in children?
We used a very simple measure, so I'm not sure I'd use screen viewing as a marker.

It's a behavior that parents could manipulate to help with problems. It's quite a specific behavior compared with physical activity. I think this is kind of a palatable message. It's feasible and achievable—and probably desirable.