You have probably seen it play out at home. Your teenager heads to bed, phone in hand, and the light under the door stays on far longer than you want. It can feel like a small habit.
On nights when a teen's phone use after 10 p.m. runs longer than their own average, they fall asleep 64 minutes later and get about 20 minutes less sleep overall.
That is the headline finding from a new study in JAMA Pediatrics, published online on October 19, 2026. The researchers are from Seattle Children's Research Institute, Columbia University and Stony Brook University.
The study tracked 425 teenagers, with an average age of just under 15, across nearly 7,600 nights of sleep.
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What each extra minute of phone use costs
Every extra minute of phone use after 10 p.m. mattered. Each one was linked to sleep onset arriving about 0.87 minutes later, and total sleep trimmed by about 0.43 minutes.
The last five minutes before falling asleep looked especially costly. Phone use in that short window was tied to more wakefulness during the night.
The study concluded that reducing evening phone use after 10 p.m., and in the final minutes before sleep, may help improve adolescent sleep.
Why screens work against the sleeping brain
The problem is not just the clock. Screens have two separate effects on the body at bedtime.
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According to the American Academy of Pediatrics, a screen can make a child more alert and raise their heart rate right when their body should be slowing down.
The light coming off the screen also disrupts melatonin, the hormone that tells the body it is time to sleep.
What parents can do tonight
The academy's practical advice is specific. Turn all screens off at least one hour before bedtime, and keep phones out of the bedroom overnight.
For teens aged 14 to 17, the academy sets the target at 8 to 10 hours of sleep a night.
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This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.