Screen time is gobbling up the lives of America’s youth, according to a new survey — and research suggests that could be a real problem in the long run.

Children ages 8 to 12 are spending almost five hours a day in front a screen while teenagers are spending nearly 7.5 hours a day on screens, according to an NBC News report on new data from Common Sense Media, a nonprofit organization that, among other things, studies children’s digital habits and rates programming for schools and families.

Those figures don’t even factor in the time kids are using screens for school or homework, where smartboards and school computers are likely a part of many classroom settings.

The more than seven hours a day teens spend on screens is a worrying number, especially when you consider research from Canada earlier this year that followed nearly 2,000 young people as they became teens.

Children who spent the most time glued to a screen when they were very young proved most at risk of developing emotional, psychological and physical health problems by the time they became teenagers, researchers at Université de Montréal in Canada reported in the scientific journal Pediatric Research.

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Those children were more likely to become depressed by age 12 or 13, to be the victims of bullying, to be aggressive, to have lower interpersonal skills, to have unhealthy diets, and to be overweight, the researchers found in the April study.

The findings suggest that very young children are missing out on key aspects of their brain development when they spend so much time staring at a screen instead of interacting with the outside world.

“ Kids who spent more time glued to a screen were more likely to become depressed, be the victims of bullying, be aggressive, to have poor interpersonal skills and be overweight. ”

Researchers closely followed the development of 1,859 children in Quebec from their birth in the late 1990s into their early teens. The study included interviews with parents and teachers as well as the children at key stages.

The study provides a cautionary tale: it was conducted before the debut of Apple’s iPhone AAPL, +3.75% in 2007 and the advent of tablets and smartphones made screens so ubiquitous. Instead, researchers looked at those who had televisions in their bedrooms from an early age, and who watched a lot of TV. Today, most kids have a screen in their bedroom, whether it’s a television, smartphone or tablet.

The new findings from Common Sense Media say many tweens and teens are flocking to YouTube GOOG, +1.16% . For example, 76% of 8- to 12-year-olds said they frequented the online video platform. Last month, federal regulators fined YouTube $170 million for collecting the personal data of viewers under age 13. The company didn’t admit liability, but said it was making changes.

Children with a television in their bedroom tended to watch about half an hour more TV per day even at preschool age, Université de Montréal researchers found. They were more likely to become overweight by the time they became teenagers and more likely to report unhealthy eating habits, data showed.

Throughout the population studied, having your own TV set when very young also predicted higher levels of self-reported depressive symptoms, teacher-reported emotional distress, victimization, physical aggression and poorer social skills.

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The Université de Montréal study was co-authored by professor Linda Pagani, a psychology professor at Université de Montréal’s School of Psycho-Education, professor Marie Josee Herbec of the university’s School Environment Research Group, and Tracie Barnett, an associate professor at the Sainte-Justine Hospital Research Center.

At first, the researchers thought there could be other factors at work. Children who spend hours in their rooms watching TV could be in troubled homes. They could have psychological problems from a very early age. They may be living in families with less parental “social capital,” including formal education.

“ The findings suggest that very young children are missing out on key aspects of their brain development when they spend so much time staring at a screen instead of interacting with the world. ”

But the “screen time” effect held true even after they controlled for these factors. Researchers say there is further work to be done to examine relationship between too much screen time and negative outcomes. The study, as always, can only point to a correlation rather than a cause and an effect.

But scientists have long understood the importance for future brain development of a child’s early years, when neural pathways expand most quickly. Too much screen time may deprive children of other, richer activities that help to hone cognitive, social, emotional and physical skills, Pagani and her co-authors wrote.

Watching a screen — whether it’s a TV, smartphone or tablet — encourages children to be more sedentary, and makes them less mindful about food if they eat while they watch, they added.

There are some important differences between TVs and tablets. Tablets are portable while big TVs are not, so if you’re watching “Frozen” over and over on your iPad, you don’t have to stay in your room or near the TV. In other words, children are more likely to spend more time gazing at a screen.

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On the plus side, computer games are more interactive than TV shows so they may engage more of the brain. Computer games are even more immersive and compelling than movies or TV. It’s eight years since author Nicholas Carr exposed in “The Shallows: What the Internet is Doing to Our Brains how too much screen time is rewiring even adult brains, and not in a good way.

As concerns around children’s apparent addiction to screens have grown, Apple has introduced controls to help parents limit the amount of time kids are on devices. Apple Chief Executive Officer Tim Cook said in 2018 that the company never intended for anyone to spend too much time on their phones, but that some people do. “Honestly, we’ve never wanted people to overuse our products,” Cook said.

Shares of Apple are up over 57% year-to-date and shares of Google are up 22%, compared to a 16% increase for the Dow Jones Industrial Average DJIA, +1.33% and a 21% increase for the S&P 500 SPX, +1.59%

This story was published on April 10, 2019 and updated on October 28, 2019.