What the research says, calmly

You're not imagining it. You're not the only one. You didn't cause this.

This page is the evidence base behind Knock, written for parents who arrive already worried. The job of this page is not to alarm you further. If you have just read The Anxious Generation in one sitting and spent the next morning Googling "is it too late": it is not too late. The job here is to lay out, in plain English, what the research actually says, with every claim linked to its primary source, and to leave the worry exactly where it found you, not worse.

Last reviewed 26 May 2026. We refresh this page every quarter against the latest Ofcom, Parentkind and peer-reviewed work.

Before we start

Three things to read first.

You did not cause this. The companies behind these apps employ behavioural psychologists, A/B testing teams, and product designers whose specific job is to make the apps very hard to put down. The fact that adult attention spans have also collapsed since 2012 is the giveaway: this isn't a parenting failure. It's product engineering, deployed against people of all ages, and your child happens to be on the receiving end of it.
You're not alone. Smartphone Free Childhood has organised over 500,000 UK parents into regional WhatsApp groups since the start of 2024. Wait Until 8th has gathered 147,000+ family signatures across the US and UK. Eighty-four per cent of UK parents whose child does not yet have a smartphone back a school-day ban. The minority is loud; the majority is on your side.
The honest position is that the evidence is correlational, not causal. We will not pretend otherwise. What follows is what the research actually shows, and where the genuine uncertainty sits. You can make a reasonable decision on this evidence. Many UK families have.

The evidence, in five numbers

What changed, where, and when.

+58%

Major depressive episodes among US adolescent girls (12–17) rose 58% between 2010 and 2017. UK trends in adolescent depression and anxiety followed a similar pattern over the same window.

Source: Jonathan Haidt and Zach Rausch, summary of CDC and NSDUH data in The Anxious Generation (book, 2024).

The honest read. This is a correlation, not a proof. The 2010–2017 window also includes social and political stressors, the cost-of-living crisis, COVID for the late part, and a general decline in unsupervised outdoor play. Researchers disagree about how much of the rise is attributable to smartphones specifically. What's not disputed is that the rise happened.

30%

of UK six- and seven-year-olds already own a smartphone. By age 12, the figure is over 90%.

Source: Ofcom Children and Parents Media Use and Attitudes Report, May 2025.

The honest read. This isn't a risk in itself. Ownership doesn't equal harm. But it does tell you something about the social context your child is living in, and the conversation you're being asked to have. The age at which "everyone has one" has moved earlier every year for a decade.

3.4×

Teenage girls who spend more than three hours a day on social media are around 3.4 times more likely to report high depressive symptoms than girls who use it less than an hour a day.

Source: Riehm et al., JAMA Psychiatry, 2019, summarised by the UK Royal College of Psychiatrists.

The honest read. Correlational. Children who are already struggling may use social media more, rather than the social media causing the struggle. Most credible researchers think both directions are happening at once. The dose-response curve (more time = more risk) is consistent across more than thirty studies.

≈40 mins

UK adolescents who use smartphones late in the evening sleep about 40 minutes less per night, on average, than those who don't.

Source: Carter et al., JAMA Pediatrics meta-analysis, 2016, and replicated in UK Millennium Cohort Study data.

The honest read. Sleep is the clearest causal lever in the research. Less sleep predicts worse mood, worse focus and worse performance the next day, and the late-evening-screen-time pattern is well-established. This is the one piece of evidence most parents already feel in their kitchen before they read the studies.

147,000+

UK and US families have signed the Wait Until 8th pledge, committing to delay smartphones until at least the end of 8th grade. Smartphone Free Childhood has organised over 500,000 UK parents in regional WhatsApp groups since January 2024.

Sources: waituntil8th.org and smartphonefreechildhood.org, both verified May 2026.

The honest read. Not a measure of harm, a measure of how many other families are doing the same thing you're considering. The minority you might feel like you'd be in if you delayed is, by these numbers, already several hundred thousand families large.

What you can actually do

Six steps, in roughly the order most families take them.

Talk to one other family. Just one. The family in your child's friendship group whose parents you already trust. Tell them you're thinking about delaying, or stepping back. You will almost certainly find they have been thinking the same thing. That's the start of a switch.
Look at sleep first. Whatever else you do or don't do, the late-evening phone in the bedroom is the single piece of evidence most parents already feel. A phone that lives downstairs after 8pm, plugged in to the kitchen, changes a fortnight.
If your child doesn't have a smartphone yet, delay. Year 6 to Year 9 is the window with the strongest research signal. The Knock Phone (£79, built on the Nokia 3210) is what most families we work with give as the first phone instead. There are five other simple phones we recommend too.
If your child does have a smartphone, step back is real. Most families we work with came in this direction. The Punkt MP02 (£295, design-led basic phone with Signal) is the typical landing place for a 13-to-15-year-old stepping back from an iPhone. We have helped over a dozen families do this. The first day looks like the end of the world. By the second weekend, it looks like a Tuesday.
Read the parent script before the conversation. The seven-moment script lives here, free. Print it. Read it twice. Don't read it aloud during the conversation, use it as your reference. Twenty minutes is enough.
Email Knock if you're stuck. hello@knockphone.co.uk. No charge, no sales call. Sometimes the right answer for a family is the Knock Phone. Sometimes it's a refurbished iPhone with Screen Time. Sometimes it's waiting another six months. We'll help you think through it.

A word on judgement

There is no judgement here.

The reason Knock exists is that the smartphone conversation has become one of the most loaded conversations in modern parenting. Parents who delay get judged by parents who don't. Parents who don't get judged by parents who do. The internet has a take. The grandparents have a take. The school has a take. The other mums at the school gate have a take.

We don't have a take on you. We have a position on the evidence, strong enough to act on, not strong enough to lecture anyone with, and a body of practical work helping UK families through the conversation. The work is most useful when it meets a parent where they are, not where someone else thinks they should be.

If you've read this far and your child has a smartphone, you are not failing. If you've read this far and you've decided to wait, you are not unreasonable. The decision is hard precisely because it's important. The fact that you're thinking carefully about it is the thing that matters.

Six questions parents ask us most about the evidence

The honest answers.

Did I cause this by giving my child a smartphone?

No. You made the same decision millions of UK parents made, for the same reasons, with the same information available at the time. The companies that built these apps spend billions of pounds on design teams whose job it is to make them very hard to put down. You were not unreasonable. You were a parent dealing with a product designed to outpace what parents can reasonably manage at home.

Is the science actually settled?

Honestly, no, and we won't pretend otherwise. The strongest evidence base is correlational, not causal. What is clear: rates of adolescent depression, anxiety, sleep problems and self-harm rose sharply across the UK, US, Canada and Australia from around 2012 onward, after smartphone use became near-universal among teenagers. There is debate about how much of that rise is caused by smartphones versus other factors. There is much less debate that something significant changed in those years.

Is it too late if my child already has a smartphone?

No. Most of the families we work with at Knock came to the conversation because their child already had a smartphone and they wanted out. Stepping back is harder than not starting, but it's done by families every week. The Punkt MP02 or a refurbished basic phone are the routes families take when stepping back. The script in the Knock kit is written for both starting and stepping back.

What about the apps my child actually uses for school?

Almost all UK school systems (Show My Homework, ClassCharts, ParentPay, Microsoft Teams for Education) work on a tablet at home or on a parent's phone. If the school insists a child must have their own smartphone during the school day, that is unusual and worth a polite email to the head of year. The Department for Education's February 2024 guidance prohibits phones across the school day, so this is the moment to ask.

Will my child be socially excluded?

There is a real cost in the first fortnight and almost none after that, in our experience. The biggest single predictor of whether the first fortnight goes well is whether one or two other families in the friendship group step out in the same window. Loneliness, not the phone, is the actual enemy here. The friend-network briefing inside the Knock kit is one paragraph designed to make that conversation with other parents simple.

What do I do if I still feel anxious about doing this?

Email hello@knockphone.co.uk. Knock reads every email and will talk you through your specific situation. There is no charge for that conversation. It is not a sales call. Sometimes the right answer for a family is the Knock Phone. Sometimes it is a refurbished iPhone with strong Screen Time rules. Sometimes it is waiting another six months. None of those is a failure.

What's at stake, in plain words

Four small things worth restoring.

We talk a lot about risk on this page because the evidence sits in studies that measure what's wrong. But the decision is also about what's right. What you're trying to give back. Knock is named after one of them, knocking on a friend's front door, which used to be how every Saturday afternoon began.

Snake. The first phone game most British people over thirty-five played. Still on the Nokia 3210. Still calming. Plays without an algorithm.
Knocking for a friend. The doorstep, the friend's nan, the negotiation in the rain. A real conversation with a real adult before the rest of the afternoon begins.
Being silly without being posted. The cartwheel on the field. The wig from the dressing-up box. Three friends laughing, nobody filming.
Finding yourself, slowly. Small private experiments, clothes, music, opinions, accents, that you try, abandon, try again, with no audience of three hundred classmates.

When you're ready, here's the next step.

Most families start with the parent script. It's free, it takes twenty minutes to read, and it doesn't commit you to anything.

Read the parent script See the phones we recommend →