Screen time for kids is probably not a problem — except at bedtime

Much has been written about the negative effects of screen time on adolescents — maybe a little too much. It turns out parents can relax, mostly. Moderate use of devices probably has pretty minimal effects on things like mental health and school achievement, but it might be a good idea to turn them off just before bed.

A study of 355,358 youths by researchers at Oxford University in the UK showed that while it's possible to find negative effects of devices on adolescents, you have to squeeze the data pretty hard to do it. They found the negative effect of devices represents only 0.4 per cent of the variation of well-being among adolescents. That is about the same result as the traumatic effect of wearing glasses. Smoking marijuana and bullying have far greater effects on overall well-being in youth, than screen time on devices.

The researchers suggest that studies looking for negative effects of devices tend to report small effects as significant, and receive a lot of attention even when the correlations are small. So the alarm about adolescents and tech is at least partly a headline-fueled "moral panic" about new technology.

The "sweet spot" for screen time

Moderation is also a key. In a previous study one of the researchers found a "sweet spot" for screen use. They found there was a "Goldilocks" zone, in which some screen time is better than none or a lot. On weekdays, the teens' well-being peaked at just under two hours for video game play and smartphone use and at around four hours of watching videos or using computers. 

But the "sweet spot" findings depend on when Goldilocks is playing with her phone. Another study of 6,616 adolescents 11 and 12-year-olds in the UK has shown that use of mobile devices an hour before bedtime had an impact on sleep quality, and the effect is more powerful if they do it in the dark.

The children completed surveys on whether or not they used mobile phones, tablets, laptops, or computer games within an hour before bedtime, as well as their actual onset of sleep, restlessness, and wake time.

Those who said they did use devices before bed were 31 per cent more likely to have poor sleep than non-users, but that likelihood jumped to a whopping 147 per cent if they used the devices in the dark.  

Previous studies have shown the negative effects on sleep quality from watching television before bed.

But the effects of using mobile devices seems to be stronger, and the result is that children are not getting the recommended nine to 11 hours of sleep they need. Any parent of an adolescent knows that if a child has a device with them in the bedroom, there is a good chance they will be on it long after lights out.

Effects of insufficient sleep 

Insufficient sleep in adolescents and children is associated with impaired immune responses, depression, anxiety and obesity. It is estimated that 87 per cent of teenagers and 59 per cent of six- through eight-graders in the United States do not get enough sleep for a variety of reasons, screen time among them. 

The power of a device to interfere with sleep goes beyond just keeping them up late. The blue light given off by the screen is believed to suppress the production of melatonin, a hormone released at night that promotes sleep. The screens are also held close to the face, which strains the focal abilities of the eyes, and when viewed in the dark, the pupils are fully dilated, allowing more of that blue light in.

Of course, if bedtime screen time has a negative effect on adolescents, you can imagine it has an effect on adults as well.

A good night's sleep can be as beneficial to your health as exercise. During sleep, the body's immune system is fortified, DNA is repaired and the brain consolidates memories. People who sleep well eat less, perform better athletically, and score better on tests.

An obvious solution to the sleep deprivation problem is to keep devices out of the bedroom, so lights out really means lights out.

And you might imagine that even though the negative effects of device use is small, there could be other benefits to turning them off a bit more. It might give you the chance to reinforce the power of face time — good old eyeball to eyeball contact — and family time. Because kids aren't the only ones with their faces stuck to their phones.