no. 03 What changed
What changed, where, and when.
≈150%
Major depressive episodes among US adolescents roughly two-and-a-half-folded between 2010 and 2021 in the national NSDUH survey, a relative rise of around 150% for both sexes. The absolute rise is steepest for girls: an additional 18% of girls aged 12 to 17 reported a major depressive episode in 2021 compared with 2010.
Source: "The teen mental illness epidemic began around 2012", After Babel, Jonathan Haidt's evidence series, charting NSDUH data; the same pattern across the UK and the Anglosphere is in the international companion post.
The honest read. This is a correlation, not a proof. The 2010 to 2021 window also includes COVID, social and political stressors, 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, and that it shows up in the same shape across the Anglosphere, including the UK.
30%
of UK six- and seven-year-olds already own a smartphone. By age 11, nine in ten children own their own mobile phone.
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.
2.4×
US adolescents who used social media for more than six hours a day were around 2.4 times more likely to report combined internalising and externalising problems than peers who used none. At three to six hours a day the figure was around double.
Source: Riehm et al., JAMA Psychiatry, 2019 (adjusted relative risk ratios 1.60 to 2.44 against non-users, ages 12 to 15, both sexes).
The honest read. Correlational. Children who are already struggling may use social media more, rather than the social media causing the struggle. Most researchers think both directions are happening at once. The dose-response curve (more time = more risk) is consistent across the studies summarised in Jonathan Haidt's evidence series.
2.2×
Children and teenagers who use a phone or tablet around bedtime have roughly twice the odds of inadequate sleep (odds ratio 2.17) and nearly three times the odds of excessive daytime sleepiness. Even a device that is merely in the bedroom, switched on but unused, raises the odds.
Source: Carter et al., JAMA Pediatrics systematic review and meta-analysis, 2016.
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 350,000 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.