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Call them what you want — Generation M (for media and multitasking), Generation Z, Post-Millennials — they’re the first generation of teenagers who were “born digital.” And, as virtually all tween TV shows remind us, kids these days can’t function without their phones: The average Gen M-er sends about 60 texts a dayNinety-seven percent of teens now have at least one electronic device in their rooms. And, in one study, more than 20 percent of teens admitted that “they almost always wake up during the night to use social media."

These sorts of stats can paint an alarming picture of teen tech use. And we know that non-stop screen time can affect various aspects of teens' health — including their sleep. But it’s not as though previous generations of teens didn’t also spend their nights staring at screens. Before Gen M-ers stayed up sending Snaps, Millennials put off bedtime with epic AIM sessions. When it comes to interfering with sleep, are smartphones really that different from their clunkier, single-function predecessors? Yes, actually. Besides fueling the mobile culture that prioritizes thumbs over tongues, our pocket-sized, do-everything devices have fundamentally altered the already confused relationship between teens, screens and sleep. 

In fact, Madeleine George, a doctoral researcher at Duke University who’s studied pre-bed tech use in teens, argues that smartphones aren’t just an updated version of yesterday’s distracting technology — they’re a game-changer in the sleep world. “This [problem] is more relevant with mobile types of technology because [adolescents] can bring [their phones] to bed with them,” said George. “It’s mobile, it’s theirs and it’s immediately available.”

Same biology, new technology

Teenagers’ tendency to stay up late is by no means a new problem. They’re biologically predisposed to be night owls: Studies have shown that puberty is marked by a delayed sleep phase. What’s more, the rapidly changing adolescent brain undergoes “neural pruning.” This means that it sheds old neural connections to make room for new connections that are needed to acquire adult traits, such as impulse control. This pruning process leaves teen brains especially susceptible to environmental influences. As a result, teens are more likely than adults to give into late-night temptations, such as hungrily scrolling through their friends' latest escapades on Instagram.

"Another issue with smart devices that is not an issue with TVs is the text messaging and social media aspect," said Erica Kenney, a research fellow at the Harvard T. H. Chan School of Public Health. "Your TV is not going to wake you up with an alert that someone has posted something new on Facebook or that you have a new text message or phone call, but your smart device can."

Along with being woken up in the middle of the night, there are other intergenerational differences distinguishing Generation M-ers from their predecessors. For one thing, they can now read, listen to, look up and watch anything their hearts desire. “Teens are interacting more with their devices … [because they] can be tailored to [their] own interests,” said George.

Gone are the days when limited entertainment options might have motivated bored teenagers to turn in for the night. Today, if a teen isn’t engrossed by their surplus of Snap stories, they can youtube and learn the latest dance moves (see: #RolexChallenge), stream Drake’s latest drop or message a friend, all using one device. “Smartphones combine the activities that used to be in separate pieces types of technology,” said George, “which may each have separate and cumulative effects on development and sleep.”

And while researchers are still looking into how much smartphone use is affecting sleep, studies suggest that on days when adolescents report more smartphone use, they also have more same-day ADHD symptoms. These effects could be bidirectional, meaning both that increased smartphone use could exacerbate existing attention problems and that new attention problems could encourage more phone use. What's more, teens with ADHD are already more likely than their non-ADHD peers to report sleeping poorly. 

A modern-day affliction 

To make matters worse, some teens see their phones as an extension of themselves. They are the blinking devices in their hands, according to research on nomophobia, a modern-day affliction that arises as a result of device separation. Research has shown that nomophobics use words associated with memory and self to describe the meaning of their smartphones, suggesting that their identity is intertwined with their phone. Unsurprisingly, there's some evidence that teens are the most nomophobic age group — they feel so obligated to respond to messages in a timely manner that, according to a 2010 Pew Research Center study, they'd rather text the night away, bleary-eyed as they might be, than face a displeased friend’s why-didn’t-you-answer-my-text text. 

What does this mean for sleep? Given how recent smartphones are, there's a limited amount of research that focuses exclusively on sleep and smartphones. But studies have shown that pre-bed use of stimulating technologies, such as cell phones, is significantly related to difficulty falling asleep, which manifests in delayed sleep onset latency, aka more time spent counting sheep before falling asleep. Video games, too, have proven to leave teens in a state of arousal. This arousal, researchers believe, likely extends to smartphones because of their gaming capabilities. And another study showed that even watching a suspenseful TV show before bed can cause increased excitement and difficulty falling asleep in teens.

Now consider a smartphone’s multifunctional abilities: The arousal level is likely compounded. "The closer our media use (and any arousal that results from it) happens to the moment when we finally try to sleep, the bigger the carry-over effect is going to be," said Jan Van den Bulck, professor of communication studies at the University of Michigan.

The pioneering chronobiologist, Russell Foster, who's at the University of Oxford, made a similar comment to Wired, saying "I suspect the main effect [of pre-bed smartphone use] is ... essentially the arousing nature of the content from smartphones." 

Blue light all night 

And of course, there’s the issue of the sleep-busting blue light emitted from device screens. When someone lies in bed at night, staring into their phone, that bright blue light suppresses the sleep-inducing hormone melatonin. And since light intensity decreases with distance, the current thinking is that televisions have a weaker effect on melatonin levels than smartphones, given how much closer they typically are to your eyes. On top of this, a study by Ann Johansson, a nurse and PhD candidate at the University of Pittsburgh, found that 10 percent of teens used more than six devices before they slept. That's a lot of light. 

To test this blue light-melatonin hypothesis, a group of researchers in South Korea gave study participants smartphones that either emitted real blue light or "sham" light that looked blue, but was actually created from different wavelengths, to play games on at night. Although these participants were adults, the ones who used the real blue-light smartphones had a later onset of melatonin release. This means that they didn't start feeling sleepy until later in the night. And, in teens, this artificially delayed sleepiness only amplifies their existing tendencies towards keeping late hours. 

It’s not all bad

We should recognize how nighttime tech use delays bedtimes and disturbs sleep, particularly in teens. But we shouldn't see smartphones as being purely an impediment to sleep. “We may be able to find ways in which technology can help people, including adolescents, with their sleep,” said George.

Specifically, George is studying how technology can be used to help first-year college students acclimate to a new environment. Since previous studies found that daily communication with parents led to better self-care among college freshmen, George was interested in seeing if using tech to communicate with parents could, in addition to helping students cope with stress, help them sleep better.

And we shouldn't place all the blame on teens and their over-pruned brains. The over-18 crowd is full of nomophobics with shoddy sleep habits. A decent chunk of the country could benefit from dialing back their bedtime phone use. Even Johnansson admits she has trouble practicing what she preaches. But, here's her easy-to-follow rule of thumb: Put away blue-lit devices one hour before bed, so that the mind and body can smoothly transition into a sleep state.


This story has been updated.