Teenagers who use smartphones, laptops, and tablets more often than their peers take longer to fall asleep and sleep for less time overall, a new study published in the journal BMJ Open shows. The finding suggests that if teenagers want to sleep better, they should try looking at screens less.
"The more you spent on devices the less you slept and the longer it took to fall asleep."
Researchers surveyed more than 10,000 16-to-19-year-olds from Norway, questioning them about their use of electronics and sleeping habits. Those who used gadgets including MP3 players, video game consoles, tablets, smartphones, and computers for more than five hours a day were three and a half times more likely to sleep for fewer than five hours at night and 49 percent likelier to need more than an hour to get to sleep. "There was a gradual increase up to this point," lead author Dr. Mari Hysing told The Verge. "The more you spent on devices during the daytime, the less you slept, and the longer it took to fall asleep."
The research confirms long-standing assumptions about the effects of electronic devices on sleep, but scientists say the exact mechanisms at work still aren’t clear. Light from electronic devices could be affecting teenagers’ body clocks, for example, or there could be less obvious effects, such as the emotional stimulation from chatting with friends.
The study questioned teenagers on their screen time both throughout the day and during the hour prior to sleep. Respondents who used computers or smartphones during this last 60 minutes before bed were 53 percent and 35 percent more likely, respectively, to miss out on two or more hours of sleep, with smaller risks reported for those using tablets, TVs, video game consoles, and MP3 players. People have different needs for sleep, but in general teenagers need eight to nine hours.
Lack of sleep is linked to everything from obesity to bad grades
And getting the right amount of sleep isn’t just important for avoiding bad moods the next day. Scientists have found links between a lack of sleep and all sorts of harmful outcomes, from obesity to lower grades in school. Overtiredness in children has even been found to predict problems with alcohol and drugs.
Although the study establishes a clear link between increased screen time and bad sleeping habits, scientists say the exact cause of disruption still isn’t clear. Previous studies have found a link between the exposure to artificial light and decreases in melatonin, the hormone that controls our body clock, but more oblique mechanisms may also be at work. For example the emotional stimulation provided by talking to friends. "As a clinician," says Dr. Hysing, "I’ve seen teenagers get worried just by mentioning a test a day after or an exam, and these worries might be triggered by social media. You might also lose the sense of control in your environment because anyone can contact you at night."
Dr. Hysing also mentions the possibility that some of the study’s observations were caused by adolescents using electronic devices as a sleeping aid when they felt too awake, or to counteract boredom at night. But they may be reaching for the wrong sleep aids, since "the relationship between poor sleep and electronic media use reflects a self-perpetuating cycle," the research says. We sleep less because we use our gadgets too much and then we use our gadgets too much because we sleep less.
there's a link between screen time and sleep, but we need lab studies to pin it down
Scientists will have to wait for controlled lab studies to find out more, says Dr. Akhilesh Reddy, a specialist in circadian rhythms at the University of Cambridge. "People have made peripheral links with things like melatonin for a marker of how light might affect sleep," he says, "But you could affect melatonin without affecting sleep."
Dr. Reddy also points out that it’s very difficult to control all the parameters in studies like this, with seemingly insignificant variables like a subject’s height playing a part. "This would mean longer arms and therefore you might get less exposure to a screen’s light," he says, adding that whatever field studies researchers conduct, "teenagers are going to be doing all sorts of things you can’t control for." Parents that are trying to make sure their children get a good night’s sleep will no doubt feel the same way.