7 Things You Should Know About How Screens Might Affect Your Health

TL;DR: You don't need to worry about endless scrolling on your iPhone ~too~ much.

We're spending more time in front of screens than ever before, and we're worried about it.

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That increase is hardly surprising, since we now carry little screens around with us at all times. According to a 2015 Ofcom report, people spent twice as much time online in 2014 as we did in 2004, at over 20 hours a week, a rise fuelled by the ubiquity of smartphones and tablets.

The rise is most dramatic among younger people. Internet use has nearly tripled among 16- to 24-year-olds, from around 10 hours a week in 2005 to 27 and a half hours in 2014.

Of course, that doesn't tell you whether screen time is good or bad. But lots of people are concerned. An article in The Atlantic by Jean Twenge last month asked: Have smartphones destroyed a generation? It said the rise in screen time has had a "dramatic" – and negative – effect on teenagers' mental health, on their social interaction, even on their sex lives. Twenge, whose claims are highly controversial, is one of several voices to have raised these concerns in recent years.

So we spoke to four scientists to see what the evidence says about how our screen habits might be affecting our health.

1. "Screen time" isn't a simple thing.

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"This idea that 'screen time' is a unitary concept really grows out of studies about TV time in the 1970s and 1980s," Dr Andrew Przybylski, an experimental psychologist at the University of Oxford's Internet Institute, tells BuzzFeed News. "It was ported over into the digital age."

But, he points out, that's not how we think about anything else: "We don't talk about paper time or food time or book time." Screen time could mean doing research on Wikipedia, or it could mean watching hardcore pornography. The effects of those two things will probably be very different. That's not to say we can't have meaningful discussions about "screen time", but it won't be a simple "it is good" or "it is bad".

2. It's ~really hard~ to do good research into it.

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There's not much evidence into the impact of screen time – either positive or negative, says Dr Suzi Gage, a psychologist at the University of Liverpool. There are several studies, but the results they give are unclear and difficult to interpret. "It's not that the studies are bad," she says. "It's that they're hard to do."

Essentially, say you looked at 10,000 people who use screens lots and lots, and 10,000 people who hardly use screens at all, and you found (say) that the people who use screens lots and lots are happier than people who don't. Does that show you that screens make you happier?

Well, no. Maybe it just happens that people who use screens a lot are happier anyway. Maybe they're richer, on average, and maybe that makes them happier. You can try to "control" for that, by comparing people against others of similar income, but there still could be something you haven't thought of. "People who use screens might be different in ways that we don't always understand," says Gage. "It's hard to know what causes a correlation."

That's a common problem in this sort of research. But it's even harder with screens, because the direction of causality can get so mixed up. If people who are socially anxious use screens more, is that because the screens are making them anxious? "Perhaps they use screens more because they find it hard interacting with people face-to-face," says Gage. If that's the case, then it could be that screens actively improve such people's social lives rather than hindering them.

There's also the problem that it may not be the screens that are the problem, but the time they're taking up. "What's difficult to know, when people are using screens more, is: What aren't they doing instead?" asks Gage. "Are they sleeping less? Are they going outside less? Are they socialising less? There could be all sorts of things they're missing out on by using screens. Untangling that from the screen time itself is hard."

3. There might be a link between screen time and mental health, but it's complex.

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Przybylski published a study in January that found that a "moderate" amount of screen time – up to a couple of hours a day on weekdays, more on weekends – was actually correlated with better mental wellbeing in teens.

Again, this might not be all that surprising. "If you've got kids who don't use screens at all, then they're not on social media," says Dr Pete Etchells, a psychologist at Bath Spa University, told BuzzFeed News. "If all their friends are on it, that means they're automatically excluded from those social groups."

If you use screens for longer than that, it does become more negative. But the effect appears to be slight. "Even at exceptional levels, we’re talking about a very small impact," said Przybylski, talking to BuzzFeed News for an earlier piece. "It’s about a third as bad as [the effect on wellbeing of] missing breakfast or not getting eight hours' sleep."

Earlier studies are also ambiguous. Gage mentioned a review of the literature, which looked at four studies of screen time and anxiety. "Two found a positive correlation, one found no correlation, one found a negative correlation." She also said there is some evidence for a correlation between depression and screen use, but again, that evidence is just not very useful for saying whether that's a cause or an effect.

4. If you're worried about it, you might want to think about the ~quality~ of your screen time, rather than the quantity.

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"In recent years people have started saying that screen time is fine as long as it's high-quality," says Przybylski. The trouble is, he says, there's no real guidance as to what that is, so we're straying out of the realm of testable, scientific hypotheses, but we can all, probably, make some commonsense assumptions about what might count as "quality" (letting your toddlers Skype their grandparents) and what probably wouldn't.

Obviously there will be some judgment calls, but this position might be better than a blanket "screens good/screens bad" one. "It strikes me, as a parent, as a pretty sensible thing," says Przybylski.

Etchells agrees: "You could draw an analogy with food. There's junk food, and there's healthy food. You don't go around saying that food is bad." He points to video games. "On the one end of the spectrum, there's something like Final Fantasy, which takes 50 hours to complete, and there's a story like an epic movie, and you only buy it once," he says.

"On the other, there are freemium games that you can download for free but are designed to earn money through microtransactions. They're endless levels that look the same, very quick to play and to win and to lose, and to tap into our impulsivity, like slot machines."

5. Like anything else, if you use screens too much, that's too much.

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"It's a commonsense thing," says Etchells, "but if you're on social media for a bit of the day, then that's fine. If you're on it for 18 hours, then that's worrying.

"Anything you do to excess is a bad thing, so it feels like a cop-out to say it, but it's everything in moderation," he says. Reading books is generally seen as a "good" thing, and if you don't read any books at all, that's probably not ideal – but if you were reading novels for 12 hours a day and not going to school or work and spending all your money on them, then that wouldn't be ideal either.

And, of course, it's what you're not doing, as much as what you ARE doing. If your screen use is stopping you getting any exercise, then that's bad – not because screens are bad, but because exercise is good.

6. You probably don't need to worry too much about the effects of screens on sleep, although it's still worth being a bit careful, especially for teenagers.

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Russell Foster, a professor of sleep science at the University of Oxford, told BuzzFeed News that there has been a "mass of hype" around sleep and screens. The idea is that the blue light of an iPhone screen (or other screen) tricks your brain into either resetting its internal clock, or becoming more alert than it should be as it winds down, by suppressing the production of a sleep-inducing hormone called melatonin. Apple have introduced a low-blue-light "night shift" feature to their iPhones, to counteract it, and at least one Premier League football team makes its players wear orange glasses for an hour before bed to help them sleep. But the evidence for it having much of an effect is "very low", Foster says.

"A study looking at ebooks, on full brightness for four hours before bedtime for five nights, found that it delayed sleep onset by 10 minutes," he said. That's nothing compared to, say, a cup of coffee. And it's hard to tell whether that was the light, or just the content. ("We all remember when we first read Jaws," he says. Books don't necessarily help you sleep.)

But as a rule, it's a good idea to avoid bright lights – including, say, going into a brightly lit bathroom – in the time before bed, he says. It's especially true for teenagers, whose body clock is naturally geared towards going to bed late and getting up late. "Anything that doesn't enhance your tiredness at that time isn't helpful." That's not screen-specific, though: "I don't read science papers or anything before I go to bed. I tend to read trashy novels, because they're easy and undemanding."

7. Overall, claims that iPhones are destroying us all are overblown.

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"People want to insist on making screens the Big Bad of society," says Etchells. "I'm not sure why it's the case. I'm sure it comes from good intentions."

The scary claims are "premature at best", says Gage. "They all say 'screens change your brain', but everything changes your brain," she says. "Of course it changes the way we interact, but so does any advance in technology. These are the identical arguments we had at the advent of television.

"I definitely don't think there's enough evidence to back up anything that strong. It's exaggerating."

So don't worry too much about your screen use. There's no good reason to think that it's bad in its own right – although, of course, like anything else, if it's taking up too much of your life, that could be a problem.