Sleep, the first thing to go

If a parent asks where to start, we say sleep. Not because it is the most dramatic thing a smartphone affects, but because it sits underneath everything else. Mood, anxiety, concentration, the ability to cope with a bad day at school. All of it rests on whether a child slept.

What the research says

The largest review on this question was published in JAMA Pediatrics in 2016. It pooled 20 studies and over 125,000 children and adolescents, average age around 14. The findings were stark. Children who used a portable device at bedtime were roughly twice as likely to get too little sleep, and nearly 3 times as likely to be excessively sleepy during the day, compared with children who did not.

The finding every parent should sit with is the next one. Children who simply had a device in the bedroom, whether or not they used it, were still around 80% more likely to get too little sleep and more than twice as likely to be sleepy the next day. Access alone was enough.

Since then, study after study has pointed the same way. The exact size of the effect is debated among researchers, as it should be. The direction is not.

Why adolescents are especially exposed

Around puberty, the body clock shifts. Teenagers naturally fall asleep later and wake later. This is biology, not laziness. School starts at the same time regardless, so most teenagers are already running short. Add a device that is designed to keep them scrolling past midnight, that lights up with a group chat at 1am, and that they feel they must respond to, and you have a child who is chronically short of sleep during the exact years when the brain is doing its heaviest building work.

What is seen in practice

A first year who is irritable and tearful by Thursday. A second year who cannot get up and is "always tired." A teenager whose anxiety is worst in the morning. When we work backwards, the phone is very often in the bedroom, and very often the last thing she looked at.

We want to be careful here. Anxiety and low mood have many causes and a phone is never the whole story. But sleep is the foundation, and a phone in the bedroom is the most common thing undermining it. It is also the easiest to change.

The bedroom rule

The single most effective thing a family can do is simple to say and hard to keep: no phones in bedrooms overnight. Not on silent. Not face down. Not "just as an alarm." Out of the room, charging in the kitchen or the hall, for every member of the household including the adults.

Families who manage this report the same thing. The first week is a fight. By the third week the child is sleeping better, and by the second month the parent notices they are sleeping better too.

Why waiting makes this easier

A basic phone that calls and texts has nothing on it to keep a child awake. It can charge in the kitchen without a battle, because nobody feels they are missing anything. The bedroom rule becomes a habit years before a smartphone arrives, and when the smartphone does come, the habit is already there. That is what a staged pathway does. It lets a family build the rules before the pressure.

One thing to do this week

Buy a cheap alarm clock. That removes the last reason for a phone in the bedroom. Then choose a charging spot outside every bedroom in the house, and use it yourself first.