We’ve all seen it – teenagers glued to their phones, not even glancing up when their parents talk to them; kids immersed in tablets at airports; young friends around restaurant tables staring at their phones instead of each other.

As children and young people spend an increasing amount of time with screens – more than six hours a day according to one US survey – parents have begun to wonder if spending this much time with screens is safe.

An increasing amount of research suggests it is not. Teenagers who spend five or more hours a day on electronic devices are 71% more likely to have a risk factor for suicide than those who spend less than an hour a day. Young people who use screens this much are also 52% more likely to sleep less than seven hours a night – a significant amount of sleep deprivation with potential consequences for both physical and mental health. The more time young adults spend on social media, the more likely they are to be depressed or lonely.

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Of course, correlation doesn’t prove causation – perhaps unhappy people use digital media more. However, several experiments and longitudinal studies have concluded that digital media use leads to unhappiness, but unhappiness doesn’t lead to digital media use.

As I document in my book, iGen (about the post-millennial generation born after 1995), there are also troubling trends in teenagers’ mental health. Between 2011 and 2015, rates of serious depression, self-injury (such as deliberately cutting oneself), and suicide all skyrocketed among American teenagers.

By far the largest change in their lives between 2011 to 2016 was growing smartphone ownership; the percentage of Americans owning a smartphone has more than doubled in that time. iGen teens, the first to spend their entire adolescence with smartphones, are in the midst of the worst mental health crisis in decades.

Here’s the twist: the people who designed these electronic devices and apps knew exactly what they were doing, and they knew that overusing them wasn’t safe, especially for children. When New York Times reporter Nick Bilton interviewed Apple co-founder and chief executive Steve Jobs in late 2010, he asked Jobs if his kids loved the iPad. “They haven’t used it,” Jobs said. “We limit how much technology our kids use at home.”

Bilton was gobsmacked, but he later discovered that many other tech experts also limited their children’s screen time, from the co-founder of Twitter to the former editor of Wired magazine. As Adam Alter put it in his book Irresistible: “It seemed as if the people producing tech products were following the cardinal rule of drug dealing: never get high on your own supply.”

Smartphone owners of all ages should be thinking about how to use their devices safely – meaning for a few hours a day, not for most of it

Sean Parker, one of the founders of Facebook, recently observed that its addictive qualities “exploit a vulnerability in human psychology … God only knows what it’s doing to our children’s brains.” Jony Ive, Apple’s chief design officer, said that “constant use” of the iPhone was “misuse”.

Until now, the primary goal of parental controls on devices was content, often focused on limiting children and young people’s access to pornography, violence, or profanity. However, content is only part of the problem – the larger issue is teenagers spending nearly all of their leisure time on their phones.

Given the consequences of overuse, setting time limits is just as important as restricting access to content. For instance, parents could limit the amount of time certain apps are used, restrict hours of total phone use, or shut the phone down after bedtime (or, even better, an hour before bedtime to avoid overstimulation before sleep).

Third-party apps can do this, but they are not integrated into the iPhone, for instance. That’s why two of Apple’s major investors wrote a letter to the company this week asking them to include better parental controls in their devices (full disclosure: I helped draft this letter, which described the research on device use and mental health).

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Limiting teenagers’ phone use might sound like the beginning of a huge parent-child fight. However, it might not be as bad as you think. When I interviewed young people for iGen, I was surprised how many were aware of the negative effects of spending so much time on a phone. Several complained, just as adults do, that they hated it when their friends or parents were looking at their phones when they were talking.

Since then, I’ve spoken to several teachers who asked teenagers to put their phones away for an hour or two for a project, either in or out of class. All said that their reactions were much more characterised by relief than anger. Teenagers often feel constant pressure to respond instantly to texts and social media posts, and welcome a break.

Should we instead adopt a cold turkey strategy and just take teenagers’ phones away? The research suggests this is not a good idea. Young people who don’t use smartphones or social media at all are less well-adjusted than teens who use them a little – perhaps because teen social life these days requires at least some digital media.

Mental health peaks at an hour a day of device use, with issues becoming more frequent among those using devices two, and especially three or more hours a day. My children (who are 11, eight and five) don’t yet have smartphones, but when they do I plan to limit their use to 90 minutes a day and shut the phone down at 9pm. As they get older, these limits can be adjusted.

Momentum on this issue is building, and I expect that parents, policymakers and tech companies will be working over the next few years to come up with workable solutions. In the meantime, smartphone owners of all ages should be thinking about how to use their devices safely – meaning for a few hours a day, not for most of it. Let your phone be a tool you use – not a tool that uses you.

• Jean Twenge is the author of iGen and a professor of psychology at San Diego State University