The first data from a decade-long study of the effects of screen time on more than 11,000 American children by the National Institutes of Health shows that those who spent more than two hours each day on screens scored lower on thinking and language tests, according to a report from CBS' "60 Minutes." 
 
 The big picture: In extreme cases, researchers also said that some brain scans of 9- and 10-year-olds who spend more than seven hours a day using electronic devices show a thinning of the brain's cortex, which usually happens later in development. It's worth noting these are early results that have not yet been published in a peer-reviewed journal, so they shouldn't be viewed as definitive. As the NIH's Dr. Gaya Dowling told "60 Minutes," "We don't know if it's being caused by the screen time. We don't know yet if it's a bad thing." ||||| The American Academy of Pediatrics now recommends parents "avoid digital media use -- except video chatting -- in children younger than 18 to 24 months" 
 
 Researchers have found "different patterns" in brain scans among children who record heavy smart device and video game use, according to initial data from a major ongoing US study. 
 
 The first wave of information from the $300 million National Institute of Health (NIH) study is showing that those nine and 10-year-old kids spending more than seven hours a day using such devices show signs of premature thinning of the cortex, the brain's outermost 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," said Gaya Dowling, an NIH doctor working on the project, explaining the preliminary findings in an interview with the CBS news program 60 Minutes. 
 
 "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," Dowling said. 
 
 The NIH data reported on CBS also showed that kids who spend more than two hours a day on screens score worse on language and reasoning tests. 
 
 The study -- which involves scanning the brains of 4,500 children -- eventually aims to show whether screen time is addictive, but researchers need several years to understand such long-term outcomes. 
 
 "In many ways, the concern that investigators like I have is, that we're sort of in the midst of a natural kind of uncontrolled experiment on the next generation of children," Dimitri Christakis, a lead author of the American Academy of Pediatrics' most recent guidelines on screen time, told 60 Minutes. 
 
 Initial data from the study will begin to be released in early 2019. 
 
 The academy now recommends parents "avoid digital media use -- except video chatting -- in children younger than 18 to 24 months." ||||| If you have kids and wonder if all that time they spend on their smartphones endlessly scrolling, snapping and texting is affecting their brains, you might want to put down your own phone and pay attention. The federal government, through the National Institutes of Health, has launched the most ambitious study of adolescent brain development ever attempted. In part, scientists are trying to understand what no one currently does: how all that screen time impacts the physical structure of your kids' brains, as well as their emotional development and mental health. 
 
 At 21 sites across the country scientists have begun interviewing nine and ten-year-olds and scanning their brains. They'll follow more than 11,000 kids for a decade, and spend $300 million doing it. Dr. Gaya Dowling of the National Institutes of Health gave us a glimpse of what they've learned so far. 
 
 Dr. Gaya Dowling: The focus when we first started talking about doing this study was tobacco, marijuana, all drugs the screen time component really came into play because we were wondering what is the impact? I mean, clearly kids spend so much time on screens. 
 
 The first wave of data from brain scans of 4,500 participants is in and it has Dr. Dowling of the NIH and other scientists intrigued. 
 
 The MRI's found significant differences in the brains of some kids who use smartphones, tablets, and video games more than seven hours a day. 
 
 "We're sort of in the midst of a natural kind of uncontrolled experiment on the next generation of children." 
 
 Dr. Gaya Dowling: 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. 
 
 Anderson Cooper: That's fascinating. 
 
 Dr. Gaya Dowling: It's very fascinating. 
 
 The colors show differences in the nine and ten-year-olds' brains. The red color represents premature thinning of the cortex. That's the wrinkly outermost layer of the brain that processes information from the five senses. 
 
 Anderson Cooper: What is a thinning of the cortex mean? 
 
 Dr. Gaya Dowling: That's typically thought to be a maturational process. So what we would expect to see later is happening a little bit earlier. 
 
 Anderson Cooper: Should parents be concerned by that? 
 
 Dr. Gaya Dowling: 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 
 
 The interviews and data from the NIH study have already revealed something else: kids who spend more than two hours a day on screens got lower scores on thinking and language tests. 
 
 Anderson Cooper: When the study is complete, is it possible that a researcher will be able to say whether or not screen time is actually addictive? 
 
 Dr. Gaya Dowling: We hope so. We'll be able to see not only how much time are they spending, how they perceive it impacting them, but also what are some of the outcomes. And that will get at the question of whether there's addiction or not. 
 
 Anderson Cooper: When will you have the answers that you're searching for? 
 
 Dr. Gaya Dowling: Some questions we'll be able to answer in a few years. But some of the really interesting questions about these long-term outcomes, we're gonna have to wait awhile because they need to happen. 
 
 That delay leaves researchers who study technology's impact on very small children anxious. 
 
 Dr. Dimitri Christakis: In many ways, the concern that investigators like I have is that we're sort of in the midst of a natural kind of uncontrolled experiment on the next generation of children. 
 
 Dr. Dimitri Christakis at Seattle Children's Hospital was the lead author of the American Academy of Pediatrics' most recent guidelines for screen time. They now recommend parents, "avoid digital media use, except video chatting, in children younger than 18 to 24 months." 
 
 "Toddlers need laps more than apps" 
 
 Dr. Dimitri Christakis: So what we do know about babies playing with iPads is that they don't transfer what they learn from the iPad to the real world, which is to say that if you give a child an app where they play with virtual Legos, virtual blocks, and stack them, and then put real blocks in front of them, they start all over. 
 
 Anderson Cooper: If they try to do it in real life, it's as if they've never done it before. 
 
 Dr. Dimitri Christakis: Exactly. It's not a transferable skill. They don't transfer the knowledge from two dimensions to three. 
 
 Dr. Christakis is one of the few scientists who have already done experiments on the influence screens have on children under the age of two. It's a critical period for human brain development. 
 
 Dr. Dimitri Christakis: If you're concerned about your teenager being addicted to their iphone, your infant is much more vulnerable and using the exact same device. 
 
 Anderson Cooper: Your infant is more vulnerable because why? 
 
 Dr. Dimitri Christakis: Because the experience of making something happen is so much more gratifying to them. 
 
 In a small pilot study that Dr. Christakis conducted on 15 children, researchers gave toddlers three toys: first a plastic guitar, then an iPad that played musical notes and finally an iPad with an app that rewarded the kids with lights, colors and sounds. 
 
 Dr. Dimitri Christakis: So at a very specific time, the research assistant will ask the child to give what they're playing with back. 
 
 Anderson Cooper: To give it to the research assistant. 
 
 Dr. Dimitri Christakis: To give it to the research assistant. 
 
 Sixty-six percent of the time with a traditional toy, the child will do just that. 
 
 Dr. Dimitri Christakis: With the iPad that simulates that, they give it back almost with the same frequency. But with the iPad app that when they push on it, it does all kinds of things, they're much less likely to give it back. 
 
 With the more interactive iPad app, the percentage of kids willing to hand it back to the researcher dropped from 60 percent to 45 percent. 
 
 Anderson Cooper: It's that much more engaging? 
 
 Dr. Dimitri Christakis: It's that much more engaging. And that's what we find in the laboratory. 
 
 It's engaging by design, as Tristan Harris told us in a story we reported more than a year ago. 
 
 Tristan Harris: There's a whole playbook of techniques that get used to get you using the product for as long as possible. 
 
 Harris is a former Google manager who was one of the first Silicon Valley insiders to publicly acknowledge that phones and apps are being designed to capture and keep kids' attention. 
 
 Tristan Harris: This is about the war for attention and where that's taking society and where that's taking technology. 
 
 Anderson Cooper: You know it's one thing for adults, for kids this is a whole other thing? 
 
 Tristan Harris: That is where this gets particularly sensitive…is developmentally do we want this war for attention to be affecting our children? 
 
 Anderson Cooper: Do you think parents understand the complexities of what their kids are dealing with? 
 
 Tristan Harris: No. And I think this is really important. Because there's a narrative that, oh, I guess they`re just doing this like we used to gossip on the phone, but what this misses is that your telephone in the 1970s didn't have a thousand engineers on the other side of the telephone who were redesigning it to work with other telephones and then updating the way your telephone worked every day to be more and more persuasive. 
 
 Until recently, it was impossible to see what happens inside a young brain when a person is focused on a mobile device. But now scientists at the University of California, San Diego have hacked that problem. 
 
 Correspondent Anderson Cooper speaks with Dr. Kara Bagot 
 
 Dr. Kara Bagot is an investigator on that $300 million NIH study. Her team is scanning teenager's brains as they follow Instagram, the most popular social media app. When we met 18-year-old Roxy Shimp, she was about to participate in Dr. Bagot's study. 
 
 Anderson Cooper: How much time do you actually spend on screens? 
 
 Roxy Shimp: I check my phone pretty regularly I'd say. 
 
 Anderson Cooper: What's pretty regularly? 
 
 Roxy Shimp: Every at least 10 to 20 minutes. 
 
 Anderson Cooper: Is that a conservative estimate? 
 
 Roxy Shimp: Probably. 
 
 She can't take her phone into the MRI because of the powerful magnets in the machine, so a mirror has been placed above her face to allow her to look across the room at a movie screen displaying images from her Instagram account. This way, Dr. Bagot can see exactly which parts of the brain's reward system are most active while using social media. 
 
 Anderson Cooper: So you can actually see a part of the brain light up when you're feeling good. 
 
 Dr. Kara Bagot: Yes, in the scanner. 
 
 Anderson Cooper: In the scanner. 
 
 Based on her data and the results from other studies, Dr. Bagot is among scientists who believe screen time stimulates the release of the brain chemical dopamine, which has a pivotal role in cravings and desire. 
 
 Dr. Kara Bagot: So you're more likely to act impulsively and use social media compulsively instead of, like, checking yourself. 
 
 Anderson Cooper: You want to keep on it to keep getting-- 
 
 Dr. Kara Bagot: The good feelings. 
 
 2017: What is "Brain Hacking"? Tech insiders on why you should care 
 
 Teenagers now spend on average four and a half hours a day on their phones. All that time has resulted in a fundamental shift in how a generation of american kids acts and thinks. 
 
 Jean Twenge: When smartphones went from being something only a few people had to something that the majority of people had, it had this really big effect on how teens related to each other. 
 
 "it should be a tool that you use. Not a tool that uses you." 
 
 Jean Twenge is a psychology professor at San Diego State University. She spent five years combing through four large, national surveys of 11 million young people since the 1960's. She discovered sudden changes in the behavior and mental health of teens born in 1995 and later, a generation that she calls "I-gen". 
 
 Jean Twenge: They're the first generation to spend their entire adolescence with smartphones so a lot of them can't remember a time before smartphones existed. 
 
 Anderson Cooper: There have been generational shifts before in the past, haven't there? 
 
 Jean Twenge: Certainly. But this one's much more sudden and pronounced than most of the others. 
 
 The iPhone was introduced in 2007. Smartphones gained widespread usage among young people by 2012. Jean Twenge says she was startled to find that in the four years that followed, the percentage of teens who reported drinking or having sex fell. But the percentage who said they were lonely or depressed spiked. It's possible other factors may have played a role, but Twenge says she wasn't able to identify any that correlated as closely as the growing popularity of the smartphone and social media. 
 
 Jean Twenge: It's not just the loneliness and depression from these surveys. It's also that ER visits for self harm like cutting have tripled among girls age 10 to 14. 
 
 Anderson Cooper: What are teens doing on their phones that could be connected to depression? 
 
 Jean Twenge: It could be anything. There's kind of two different schools of thought on this. That it's the specific things that teens are doing on their phones that's the problem. Or it could be just the sheer amount of time that they're spending on their phones that is the problem. 
 
 Correspondent Anderson Cooper with Jean Twenge 
 
 Finding definitive answers about social media's influence on mental health can be a frustrating exercise. Eighty-one percent of teens in a new national survey by the Pew Research Center said they feel more connected to their friends and associated social media use with feeling included. But in a month-long experiment at the University of Pennsylvania, college students who limited themselves to just 30 minutes a day on Facebook, Instagram and Snapchat reported significant decreases in loneliness and depression. 
 
 Jean Twenge: A lot of times with these technological shifts is these things are adopted because they're so wonderful and convenient. And we don't realize until later the possible consequences. And I think fortunately in the last year or so there's been more discussion about how can we manage the use of our devices. 
 
 Facebook and Instagram have introduced settings to allow users to monitor app use. And Apple, the company that started the smartphone revolution, has built a new feature for parents to set time restrictions on apps. 
 
 Anderson Cooper: Tech companies say there are tools out there that they have supplied and that they're doing their part. 
 
 Jean Twenge: A lot of parents, probably the majority I talk to, don't even realize those tools are available. and I wish they happened five years ago instead of now. But better late than never. 
 
 For its part, the National Institutes of Health has just finished enrolling the 11,000 kids for its landmark brain study. Early next year, the data will be made available to any researcher around the world investigating the effect of a device that's become the most dominant technological presence in young lives. 
 
 Jean Twenge: Smartphones are great things, They are a wonderful piece of technology. They allow us to find our way around and look up the weather and do all that kind of stuff. And if you do it for a half an hour or an hour a day, fine. No problem. Then you're using it for what it's good for. But you have to use it for what it's good for and then put it down. I mean, it should be a tool that you use. Not a tool that uses you. 
 
 Produced by Guy Campanile and Andrew Bast. Associate producer, Lucy Hatcher ||||| Image copyright Thinkstock 
 
 A study of screen time and mental wellbeing among teenagers has suggested moderate use of devices may be beneficial in a connected world. 
 
 The researchers collected self-reported data from 120,000 English 15-year-olds about their digital device habits. 
 
 They found a "Goldilocks effect" where a few hours of device-use seemed to boost mental wellbeing. 
 
 One developmental psychologist welcomed the paper but said there was still room for more study. 
 
 "Moderate engagement in digital activities is not harmful," notes the paper, published today in the journal Psychological Science. 
 
 In addition, the first hour or two of screen time was actually associated with an increase in mental wellbeing for those using computers, smartphones, video games and watching TV or films. 
 
 'Goldilocks effect' 
 
 Weekday use with a positive effect on wellbeing was described as follows: 
 
 Playing video games: One hour 40 minutes 
 
 Using a smartphone: One hour 57 minutes 
 
 Watching TV and films: Three hours 41 minutes 
 
 Using computers: Four hours 17 minutes 
 
 The effect was boosted at weekends, with the peak lasting up to four hours and 50 minutes when watching TV. 
 
 However, after this point a negative effect was reported. 
 
 The authors describe this as a "Goldilocks effect" - referring to the version of the fairy story in which Goldilocks discovers, for instance, that the best porridge is neither too hot nor too cold. 
 
 Young people's screen time has increased with the rise of digital devices used at home. 
 
 For example, children - including pre-schoolers aged three and four - are spending eight hours and 18 minutes a week online on average, according to a recent report by Ofcom. 
 
 Image copyright Thinkstock Image caption According to an Ofcom report last year, more children are now spending more time online than watching TV 
 
 Their research stemmed from a larger survey about the habits of nearly 300,000 English 15-year-olds, explained co-author Andrew Przybylski at the University of Oxford. 
 
 "We found that the negative effect of screen time was about a third of the size as not getting regular sleep or a regular breakfast," he told the BBC. 
 
 But Dr Przybylski acknowledged that most children don't simply use one device during the day - and in fact often use more than one concurrently, such as when texting a friend while watching TV. 
 
 'Choose your battles' 
 
 He suggested that rather than totting up screen time and demanding that children stop using a device after a certain point, it might be more beneficial to negotiate longer sessions and suggest alternative activities when appropriate. 
 
 "It's not so much that it's bad for a kid to play Minecraft for 12 hours on a Sunday, it's that as parents we often don't have a valued activity that we put in place of that," he said. 
 
 "It's much more important that the parents focus their limited attention and resources on picking smart battles - that might be more important than having an arbitrary cut-off." 
 
 Image copyright Thinkstock Image caption Spending too much time on the computer or watching TV may be harmful 
 
 The paper's results on the "Goldilocks effect" were welcomed by Sue Fletcher-Watson, a developmental psychologist at the University of Edinburgh. 
 
 "I think that is quite new - at least, previously, it's only been a hypothesis. 
 
 "It's really nice to have concrete evidence on that idea," she told the BBC. 
 
 However, she said there were still questions about how using digital devices affects children over time. 
 
 "One of the categories they look at is using smartphones - but that covers a huge variety of activities," she said. 
 
 If an activity exposes a child to trolling or cyberbullying, then it would naturally be likely to have a more negative effect on mental wellbeing, she suggested. 
 
 Letter wars 
 
 On Christmas Day last year, an open letter was published in the Guardian by a group of educators and psychologists that called for better guidelines, since screen-based lifestyles might harm children's health. 
 
 This was followed in January by a another open letter - co-signed by Dr Przybylski and others - that argued more evidence was needed before the full effects of children's use of screens was understood. 
 
 Image copyright Thinkstock Image caption Children today often use a range of devices - from video game consoles to smartphones 
 
 "I do feel there needs to be much clearer guidance available," said Prof Jayne Osgood at Middlesex University, a signatory of the first letter. 
 
 "Parents and educators feel ill-prepared to know what is an appropriate amount of exposure to screen time for children." 
 
 In 2013, a Public Health England briefing paper warned that too much time in front of screens combined with a sedentary lifestyle was harming children's wellbeing and increasing their anxiety. 
 
 "A few simple steps, like regular physical activity and spending time together as a family at breakfast and dinner, can minimise young people's screen time and support their wellbeing," said Eustace de Sousa at Public Health England, reacting to today's research. ||||| Young people who spend more than seven hours a day staring at a screen have different brain structures compared to the average child, according to a landmark US study. 
 
 The research, funded by the National Institute of Health and led by the University of California, San Diego, found children who spend more time online have premature thinning of the cortex, the brain's outermost layer that processes sensory information. 
 
 “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,” researcher Dr Gaya Dowling told 60 Minutes. 
 
 Scientists are still not clear... ||||| US doctors discourage videos for babies under two 
 
 WASHINGTON — Like 90 percent of American parents, Matthew Sullivan allows his infant daughter and five-year-old son to watch television, videos and sometimes web-streamed content on his smartphone. 
 
 He usually limits their screen viewing to just over an hour a day, and admits that handing his phone to his 16-month-old daughter so she can watch a YouTube video can keep her busy and quiet while they run errands together. 
 
 "We know it's not great for them, but it's not bad either," Sullivan, a 36-year-old editor in Wilmington, Delaware, told AFP. 
 
 Over the past decade, media has pervaded the developed world to such an extent that the American Academy of Pediatrics on Tuesday issued its first guidelines since 1999 to discourage any screen time for kids under two. 
 
 The largest US pediatricians' group says some of the 50 or so studies on the topic have shown that screen viewing can be linked to slower language development. 
 
 In a new twist, it also warned parents to be aware of the negative effects their own screen-watching can have on their children. 
 
 "I like to call it secondhand TV," said pediatrician Ari Brown, who is the lead author of the AAP guidelines, in an interview with AFP. 
 
 "When the TV is on, the parent is talking less. There is some scientific evidence that shows that the less talk-time a child has, the poorer their language development is," she said. 
 
 "Clearly, no one is listening to this message. In this ubiquitous screen world, I think we need to find a way to manage it, and make it a healthy media diet." 
 
 The latest guidelines do not refer to interactive play such as video games on smartphones or other devices, but to media watched passively on any kind of screen, be it phone, computer, television or other. 
 
 "This updated policy statement provides further evidence that media -- both foreground and background -- have potentially negative effects and no known positive effects for children younger than two years," it said. 
 
 "Thus the AAP reaffirms its recommendation to discourage media use in this age group." 
 
 Brown also said the update to the guidelines was needed because of the explosion of baby DVDs targeting the 0-2 age group. 
 
 "Some of these programs have good content, but even 'Sesame Street' for a kid under two is not promoting learning because they don't understand it," she said. 
 
 The AAP did not name specific products, but a host of DVDs aimed at babies and preschoolers make up a $200 million annual market in the United States, where one third of children have a TV in their bedrooms by age three. 
 
 Efforts by federal authorities to stop marketers from making educational claims on their products have fallen short, the AAP said. 
 
 "The educational merit of media for children younger than two years remains unproven despite the fact that three quarters of the top-selling infant videos make explicit or implicit educational claims," the AAP said. 
 
 One popular brand, Baby Einstein, was sold by its founders in 2001 to Disney. After studies debunked claims of intellectual benefits, Disney removed the word "educational" from marketing materials and in 2009 offered refunds. 
 
 Disney did not respond to a request for comment, but Baby Einstein founder William Clark said he was aware of "the ongoing effort to demonize the brand." 
 
 Clark told AFP that the initial mission was "to expose babies to classical music, poetry, colors in art and nature, and common animals," and "offered parents a number of ways to interact with their babies." 
 
 The product's website now carries the disclaimer: "Baby Einstein products are not designed to make babies smarter." 
 
 No studies have followed heavy television watchers into later childhood or adulthood, so any long-term effects are not known. Heavy media use is defined as a household in which the television is on all or most of the time. 
 
 The AAP guidelines point out that research to date suggests a "correlation between television viewing and developmental problems, but they cannot show causality." 
 
 Nevertheless, pediatricians should talk with parents about avoiding videos for babies and limiting screen time to no more than two hours a day for kids over two, the AAP said. 
 
 "Unstructured playtime is more valuable for the developing brain than any electronic media exposure," it said. 
 
 Sullivan said he limits his kids' viewing, not because a doctor told him to, but out of common sense. 
 
 "My son is a zombie when he watches television. If the television is not on when I come home, he runs and hugs me. If the television is on when I come home, he just doesn't even acknowledge my existence," he said. 
 
 "So obviously we'd rather he not stay in that zone for hours a day." 
 
 Copyright © 2011 AFP. All rights reserved. More » ||||| Image copyright Getty Images Image caption Correlations between screen time and lack of sleep are "extremely modest", says the report 
 
 The amount of time children spend on devices has little effect on how long they sleep, a study from Oxford University suggests. 
 
 It runs counter to previous research that suggested excessive screen time was linked to children failing to get sufficient rest. 
 
 The survey concluded that the relationship between sleep and screen use in children was "extremely modest". 
 
 But one UK GP said the findings did not tally with his clinical experience. 
 
 The study, conducted by the Oxford Internet Institute, relied on data from a 2016 US study into children's health, in which parents from across the country completed surveys about their households. 
 
 The children's "digital screen time" was based on answers to two questions about the weekday habits of children aged between six months and 17 years: 
 
 how much time they spent on computers, mobile phones, handheld video games and other electronic devices 
 
 how much time they spent in front of a TV watching programmes and other content as well as playing video games 
 
 The findings indicate that the tech-abstaining teenagers slept only slightly longer than their counterparts who had spent much of their day in front of a screen. 
 
 For example, teenagers who had not been in front of a screen for any part of the day got a total of eight hours and 51 minutes of sleep. 
 
 Those who had spent eight hours of their day glued to a screen got eight hours and 21 minutes of slumber. 
 
 The sample size for the survey was more than 50,000 youngsters from every state in the US. 
 
 'Mini case of jet lag' 
 
 The study, published in the Journal of Pediatrics, said every hour of screen time was linked to between three to eight fewer minutes of sleep a night. 
 
 Screens are now a fixture of modern childhood and both professionals and parents are increasingly expressing concerns that the amount of time children devote to devices affects their physical and mental health. 
 
 When it comes to sleep, there are concerns that children take devices to bed and continue to use them when they should be sleeping. 
 
 Others have expressed worries about the role the blue light emitted from such devices plays on sleep habits and a related hormone. 
 
 The US National Sleep Foundation has told parents that it is important to stop children using electronic devices before bedtime "because the blue light emitted from these screens can delay the release of sleep-inducing melatonin". 
 
 "This is an especially big problem for teens whose circadian rhythms are already shifting naturally, causing them to feel awake later at night. The end result: sleep-deprived or poorly rested kids who have essentially given themselves a mini case of jet lag," it writes on its website. 
 
 'Imperfect data' 
 
 But the study author thinks other factors should be considered. 
 
 "Focusing on bedtime routines and regular patterns of sleep, such as consistent wake-up times, are much more effective strategies for helping young people sleep than thinking screens themselves play a significant role," said study author Prof Andrew Przbylski. 
 
 Prof Przbylski told the BBC that many of the studies suggesting links between screen time and lack of sleep had very small sample sizes and need "much larger studies" to find conclusive evidence of a problem. 
 
 "Because the effects of screens are so modest, it is possible that many studies with smaller sample sizes could be false positives - results that support an effect that in reality does not exist," he said. 
 
 He acknowledged that the data used in the study was "imperfect" because it relied on reports from parents. A further study into the time that children turn off their devices before bedtime will be published shortly. 
 
 Many of the large technology firms, including Apple, Google and Facebook, have introduced dashboards allowing people to keep a check on the amount of time they spend on screens. 
 
 Some leading technology executives have banned their own children from using devices. 
 
 The late Apple chief Steve Jobs's young children were notably not allowed iPads. 
 
 Microsoft co-founder Bill Gates banned phones until his children were teenagers. 
 
 And Tim Cook, Apple's current leader, has said he would not let his nephew join social networks. 
 
 One UK GP, Rangan Chatterjee, said the Oxford University study was "welcome" but that he did not plan to change his advice to parents, which was to turn off devices an hour before bedtime. 
 
 "The more research on this area, the better because screens are here to stay," he told the BBC. 
 
 "But the findings don't replicate what I see in clinical practice which is that the use of screens right before bed has a significant impact on the quality of sleep."
– Sunday night's 60 Minutes report on screen time and kids has parents buzzing: "Heavy screen time appears to impact children's brains," reads a sample headline making the rounds. The report looked at the National Institutes of Health's Adolescent Brain Cognitive Development (ABCD) study, in which more than 11,000 9- and 10-year-olds will be followed for a decade "to see how childhood experiences impact the brain," per Bloomberg. The study began in 2013. 60 Minutes reported on the "first wave of information" from the study, which involved brain scans of 4,500 children, per AFP. Some key findings: children who spend more than seven hours per day on screens may experience premature thinning of the cortex, the outermost layer of the brain that processes sensory information, and kids who spend more than two hours per day on screens score lower on thinking and language tests. But the Telegraph notes that the second finding came from an observational study, meaning it wasn't possible to prove a link between the extra screen hours and the lower cognitive skill scores, and as for the premature cortical thinning (a natural process that typically happens in later development), "we don't know if it's being caused by the screen time," a researcher explains. "We don't know yet if it's a bad thing." Axios notes that these are preliminary results that have not been published in a peer-reviewed journal, and at the New York Times, science reporter and author Benedict Carey notes that the early results from the NIH study are actually a "mixed bag." Researchers, he says, have yet to find hard evidence of screen time causing "meaningful" changes to the adolescent brain. For 60 Minutes' full report, including outside experts talking about screen time, see here. (Here's one thing you may not have to worry about when it comes to screens.)