Screen time is a common battlefront between parents and children, from toddlers to teens alike. Desperate parents may appease a screaming 2-year-old with a video or game on their phone. And one 13-year-old told CNN that when her phone gets taken away, “I literally feel like I’m going to die.”

A comprehensive study of 4,500 children conducted by the National Institutes of Health in 2018 shows that children who spent more than seven hours a day staring at screens showed evidence of premature thinning of their brain's cortex — the outer layer that processes sensory information.

"We don't know if it's being caused by the screen time. We don't know yet if it's a bad thing. It won't be until we follow them over time that we will see if there are outcomes that are associated with the differences that we're seeing in this single snapshot," Dr. Gaya Dowling of the National Institutes of Health told CBS News. "What we can say is that this is what the brains look like of kids who spend a lot of time on screens. And it's not just one pattern."

But children can't be completely to blame for their screen addiction.

Sometimes, the parents who complain about the role of screens in family life are just as guilty of spending too much time in front of one. A 2016 study conducted by Common Sense Media found that parents spend up to nine hours a day in front of screens — and only two of them are for work-related reasons. While 78 percent of parents said they believed they were good screen time role models, the study found a disconnect between their behavior and their perception of their behavior.

But parents need to limit screen time for themselves and especially for their kids — even if it means playing the bad guy. Our mental and physical health depends on it.

Screen time recommendations by age

The American Academy of Pediatrics says children under 2 shouldn't have any screen time. But that recommendation may soon change. The American Academy of Pediatrics says children under 18 months old shouldn't have any screen time, save for video-chatting with a relative or family friend. (Photo: Tomsickova Tatyana/Shutterstock)

In recommendations issued in October 2016, the American Academy of Pediatrics (AAP) recommends no screen time at all for children under 18 months old, unless they're video-chatting with a relative. This is a change from the previous recommendation of no screens at all for children under 2. Should parents decide to introduce media after 18 months old, the AAP says "parents ... should choose high-quality programming, and watch it with their children to help them understand what they're seeing."

It's not just the level of programming that's a concern. A new study found that the more time children under age 2 spend on handheld screens, the more likely they are to have speech delays.

"I believe it's the first study to examine mobile media device and communication delay in children," Dr. Catherine Birken, the study's senior investigator and a pediatrician and scientist at the Hospital for Sick Children in Toronto, Ontario, told CNN. "It's the first time that we've sort of shone a light on this potential issue, but I think the results need to be tempered (because) it's really a first look."

For children ages 2 to 5, the AAP recommends limiting screen time to one hour a day of "high-quality programs," and the organization says parents should co-watch with this age group, too.

And for kids older than 6, the AAP encourages parents to place "consistent limits" on the time spent using media and make sure screen time doesn't take the place of physical activity or sleep. (And adults would do well to heed the same rules.)

The physical effects of screen time

Obesity. Sitting in front of a television or computer is a “sedentary behavior,” the American Medical Association says, which means it doesn’t burn much energy. Considering tweens in the U.S. stare at screens for more than four hours a day and teens up to seven hours, according to Common Sense Media, that’s a lot of sitting. In fact, fewer than four in 10 children meet both the physical activity recommendations and the screen time recommendations from the AAP.

Kids staring at tablets, phones and television screens Tweens in the U.S. spend at least four hours a day in front of a screen, even though the American Academy of Pediatrics recommends only an hour or two of screen time a day. (Photo: Brocreative/Shutterstock)

Sleep loss. Screens and that lack of physical activity affect their sleep, too. A 2014 study showed a connection between “excessive screen time and shorter sleep durations [which] are predictive of behavioral and social problems, poorer academic performance, and health conditions such as obesity.”

Hand pain. Not to mention the damage texting and gaming on our phones can do to our poor hands. A 2015 study in the journal Muscle & Nerve found that college students with high phone usage have more impaired hand function, thumb pain and repetitive-strain injuries than students who used their phone less.

Headaches. A 2016 study published in the Journal of Neurology and Psychology showed that complaints of headaches were higher in people who used their phone a lot than people with low phone usage. And headaches were longer and more frequent in heavy phone users, too.

The mental effects of screen time

Anxious teenage girl looking at smartphone The more teens look at social media, the more distressed they become, one study found. (Photo: SpeedKingz/Shutterstock)

Obsessive behavior. CNN conducted a study in 2015 of how teens use social media by analyzing the social media accounts of 200 eighth graders across the U.S. (with their permission). The study authors found that the more kids checked social media, the more distressed they became. And some checked their accounts more than 100 times a day! Child clinical psychologist Marion Underwood, the study's co-author, told the network:

"This is an age group that has a lot of anxiety about how they fit in, what they rank, what their peer-status is. There is fear in putting yourself out there on social media and they hope for lots of likes and comments and affirmations but there is always the chance that someone could say something mean.

“I think they're addicted to the peer connection and affirmation they're able to get via social media. To know what each other are doing, where they stand, to know how many people like what they posted, to know how many people followed them today and unfollowed them ... that I think is highly addictive."

Negative influences. The AAP says increased exposure to television or computers may influence a child's opinion about things like junk food, alcohol, tobacco use or aggressive behavior. For example, the food in commercials aimed at kids is often high in sugar, fat or salt. And for older kids, video game ads and movie trailers may glorify violence.

Attention disorders. Smartphones can cause attention problems in kids of all ages. A 2018 survey of more than 4,500 children between the ages of eight and 11 shows that children who spent more than two hours a day staring at screen performed worse on memory, thinking and language tests. However, the study doesn't say explicitly if too much screen time or the absence of other activities is the reason for lower test scores. "You don’t know which is the chicken and which is the egg here,” Dr. Michael Rich of Boston Children’s Hospital told Science News. "It could be that smarter kids are less likely to spend lots of time on screens."

Parents’ own phone use can also contribute to their children’s attention issues. A small 2015 study showed that when parents stop focusing on or playing with a baby to turn to their phone screen, the baby may mimic that behavior by playing with toys (or screens) for only a short period of time.

And another 2015 study showed that in people of all ages, including teens, heavy internet and phone users are more likely to lose concentration, forget information, have poor spatial awareness and make mistakes — even at times when they’re not connected to the internet or using their phones. These “cognitive failures,” as the study’s author calls them, may include missing appointments, failing to notice signs on the road, daydreaming during conversations and forgetting why they went from one part of the house to another.

Tips for reducing screen time

Create a family media plan. "Families should proactively think about their children's media use and talk with children about it, because too much media use can mean that children don't have enough time during the day to play, study, talk, or sleep," said Jenny Radesky, MD, FAAP. "What's most important is that parents be their child's 'media mentor.' That means teaching them how to use it as a tool to create, connect and learn." This video explains how to use the AAP's online tool to create a family media plan:

Put down your own phone. "Demonstrate your own mindfulness in front of your children by putting down your phone during meals or whenever they need your attention," David Hill, chairman of the AAP Council on Communications and Media and a member of the AAP Children, Adolescents and Media Leadership Working Group, told NPR.

Praise their 'offline' behavior. When you see them riding a bike or coloring, tell them how much you like what they're doing and ask them questions about it. "These conversations will help them focus on the joys of the 'real' world, and they will notice that their activity attracts your attention," Hill said.

Set limits, and stick to them. As you decide on limits, ask your kids what they think is fair. Even if you don't use their suggestions, asking them helps them feel heard and gives them input. And if they break the rules, enforce the punishment you set forth when making the house rules. Maybe they have to do more chores. Maybe their phone gets taken away. Whatever it is, stick to your guns.

Trim TV time. Don't keep televisions in children's bedrooms. Don't let kids watch TV during meals or while doing homework. And don't keep the TV on for background noise. If you're going to watch a show, decide on the show ahead of time and turn off the TV when it's over.

If you can't reduce, at least monitor closely. One surprising — and welcome! — finding from that CNN study was this: "Almost all parents — 94 percent — underestimated the amount of fighting happening over social media. Despite that finding, parents that tried to keep a close eye on their child's social media accounts had a profound effect on their child's psychological well-being." One expert even said that parental monitoring "effectively erased" the negative effects of their kids' online conflicts.

Editor's note: This story has been updated since it was originally published in June 2016.

Angela Nelson ( @bostonangela ) is an exhausted mom of two young daughters and two old cats, and a Pulitzer Prize-winning digital editor with more than 15 years of experience delivering news and information to audiences worldwide.

How much screen time is too much for kids?
From toddlers to tweens and teens, glowing screens can harm their bodies and minds. Here's how to reduce screen time, and why you should.