Smartphones are changing the way children’s brains work, according to shocking new research.
Youngsters who spend more than two hours in front of a screen are scoring lower on language and thinking tests.
Alarmingly children who spend more than seven hours a day on electrical devices are also showing premature thinning of the brain cortex, which typically happens later in development.
Previous studies have linked a thinning cortex with lower IQ levels.
The results are the first from an ambitious $300,000,000 US study that will track the brain development of 11,000 children over a decade.
Experts say we won’t know the true effects of smartphones and other technologies on developing brains until the group reach adulthood.
However their initial findings are worrying for any parent whose child endlessly scrolls or texts.
Children aged nine and ten who spent more than seven hours a day on digital media had significantly different patterns than their peers who spent less time looking at devices.
Dr Gaya Dowling, from the National Institutes of Health, said: ‘We don’t know if it’s being caused by the screen time. We don’t know yet if it’s a bad thing.
‘What we can say is this is what the brains look like of kids who spend a lot of time on screens. And it’s not just one pattern.’
Previous results from the same study of adolescent brain development showed that children who spent more than two hours a day on screens achieved lower scores in reasoning and language tests.
Psychologist Jean Twenge said: ‘This large amount of time spent using digital media is enough to crowd out time once spent on other activities, such as interacting with friends face to face, reading or going out.
‘And unlike the [old] telephone, digital media apps are designed to hook you.’
Her own research has shown that sleep quality was also affected by time spent on a smartphone or tablet.
Among teens ages 14 to 17, those who spent four or more hours a day on portable electronic devices – versus no time – were 44 percent more likely to not sleep enough.
Dr Twenge noted that sleep deprivation levels began to peak after 2012 – just as smartphone use became common.
That could be because youngsters are using the devices into the night.
However the quality of sleep is also an issue as children using screens take longer to get into a deep sleep.
This is because the blue light emitted by electronic screens tricks our brains into thinking it’s still daytime, and then we don’t produce enough of the sleep hormone melatonin to fall asleep quickly and get high-quality sleep.
Dr Twenge, wrote in The Conversation: ‘So what is a parent – or anyone who wants to sleep well – to do?
‘First, it’s best for smartphones and tablets to stay out of the bedroom after “lights-out” time.
‘Nor is it a great idea to use the devices within an hour of bedtime, as their blue light influences the brain’s ability to produce melatonin.
‘Finally, as a general rule, two hours a day or less spent on portable devices is a good guideline. These rules apply to parents, too – not only kids.’
At the same time, Dr Twenge noted that in the years after the smartphone became popular, the number of teenagers drinking or having sex fell.
However the percentage of teens who said they were lonely or depressed has rocketed.
Dr Twenge added that people born after 1995 are the first to spend their entire adolescence on smartphones and tablets.
She said: ‘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.’