Yes, late phone use is linked with later, shorter teen sleep. In a JAMA Pediatrics study published 19 October 2026, 425 US teens wore Fitbits for 7,591 nights. On nights they used their phones more than usual after 10 PM, they fell asleep about 65 minutes later on average and slept about 20 minutes less.
Key takeaways
- A cohort study in JAMA Pediatrics (Zhao, Hale and Christakis, published 19 October 2026) matched app-tracked phone use with Fitbit sleep data for 425 US teens, average age 14.8, across 7,591 nights.
- On nights with more phone use after 10 PM than a teen’s own average, sleep began about 65 minutes later and lasted about 20 minutes less, on average (unadjusted figures).
- Phone use in the last 5 minutes before falling asleep was linked with slightly more time awake after falling asleep, mostly in the first 30 minutes.
- The one change: give the phone its own bedtime. Charge it outside the bedroom, about an hour before lights-out and no later than 10 PM.
Does using a phone late at night delay teen sleep?
Yes, on average. In the 2026 study, the more a teen used the phone after 10 PM compared with their usual evening, the later they fell asleep and the less they slept that night.
Yihong Zhao of Columbia University, Lauren Hale of Stony Brook University and Dimitri Christakis of Seattle Children’s Research Institute analyzed data from the Adolescent Brain Cognitive Development (ABCD) Study, a long-running US study of brain development. They included 425 teens (51% girls, average age 14.8) with Android phones running a research app that logs phone use, who had at least 14 days of phone data alongside Fitbit sleep data, collected between late 2020 and early 2024.
| On nights with more late phone use than usual | Average difference |
|---|---|
| Time falling asleep (unadjusted) | about 65 minutes later |
| Total sleep (unadjusted) | about 20 minutes less |
| Each extra minute after 10 PM (adjusted) | sleep onset about 0.9 minutes later, total sleep about 0.4 minutes shorter |
| Phone use in the last 5 minutes before sleep | about 0.7 more minutes awake after falling asleep, mostly in the first 30 minutes |
Wake-up time moved later too, but by less than half as much (about 0.4 minutes per extra minute of late use, adjusted), so later nights were linked with shorter sleep.
Why does phone use after 10 PM matter so much?
Because in this study, late phone minutes tracked closely with later sleep: each extra minute after 10 PM was linked with sleep onset about 0.9 minutes later. Checking cutoffs hourly from 8 PM to midnight, the researchers found the links grew steadily the later the use happened.
Likely reasons: phone time displaces sleep, feeds and notifications keep the brain alert, and evening light can shift the body clock. Daniel Bigman, a child and adolescent psychiatrist and sleep medicine physician at Northwell Health who reviewed the findings, summed it up to HealthDay News:
“In short, the study did show that it kind of pushes bedtime later, and it makes it harder to transition into a stable sleep”
How much late use is typical? A separate cross-sectional JAMA Pediatrics research letter from the same ABCD Study, published in 2026, found that 657 teens aged 13 to 18 used their phones for an average of 50.1 minutes between 10 PM and 6 AM on school nights, mostly on social media apps, with a wide range between teens.
What are the limits of the 2026 study?
It shows an association, not cause. Comparing each teen with their own average accounts for stable differences between people, but it can’t rule out that a teen who isn’t sleepy on a given night reaches for the phone, rather than the phone keeping them up.
Everyone used Android phones, sleep came from consumer Fitbits rather than a sleep lab, and two of the authors disclosed paid work as experts in social media litigation, outside this study. The findings still line up with earlier work: a 2026 ABCD cohort study that followed 1,959 youths from about age 13 to 14 found that placing smartphones outside the bedroom at bedtime was linked with 36% lower odds of sleeping less than 8 hours a night.
How much sleep do teens need?
Teens aged 13 to 18 need 8 to 10 hours of sleep per 24 hours, according to the American Academy of Sleep Medicine. With a fixed school wake-up, every minute bedtime slips comes out of that window.
For more on teen sleep and school, read Do Later School Start Times Help Teens Sleep More?.
What is the one change to make?
Give the phone its own bedtime: charge it outside the bedroom, about an hour before lights-out and no later than 10 PM. It targets both findings: late use and the last minutes before sleep.
- Pick a charging spot outside the bedroom, such as the kitchen counter or a hallway shelf.
- Set the phone’s bedtime about an hour before lights-out. For a 10 PM bedtime, that is 9 PM.
- Use a basic alarm clock in the bedroom, so the phone isn’t needed for the morning.
- Fill the last hour with something calm: a book, music or stretching.
- Keep the same plan on weekends where you can, so the body clock doesn’t drift. See How to Fix Your Sleep Schedule: Anchor, Light, 15 Min.
Bigman suggests encouraging calmer wind-down activities, such as reading, music or stretching, rather than threatening to take the phone away. Docking every phone in the household in one spot makes it a family habit rather than a punishment. Curious when your own body clock runs best? Take the Body Clock Type quiz.
Your day on My BodyClock
The day above on My BodyClock shows a school day for a teen built around a phone bedtime. Sleep runs from 10 PM to 6:45 AM, 8 hours and 45 minutes, inside the 8 to 10 hours teens need. Breakfast and a walk to school in daylight lead into classes and afternoon sports practice. Homework comes before family dinner, with friends and phone time from 7:30 PM. At 8:30 PM a short pink Flow block packs the bag and docks the phone in the kitchen. The last hour is a lamp-lit Relax block before lights-out at 10 PM. For more on structuring a student day, see How to Make a Daily Schedule for College and How to Plan a Midterm Day on My BodyClock.
Set a phone-dock block with its own alert and build your version in Owaves: My BodyClock on the App Store, or join the Android waitlist.
FAQ
What time should teens stop using their phones at night?
The 2026 JAMA Pediatrics authors suggest that cutting back after 10 PM and in the last minutes before bed may help. Links with later sleep grew steadily as the cutoff moved from 8 PM to midnight, so the latest use carried the strongest links. A practical version: dock the phone outside the bedroom about an hour before lights-out, and no later than 10 PM.
Does phone use before bed really cause bad sleep?
This study shows a link, not proof of cause. It tracked the same teens across many nights and found later, shorter sleep on their heavier late-phone nights, which rules out some differences between people, but a teen who isn’t sleepy may also simply pick up the phone. A separate 2026 study found that keeping phones out of the bedroom was linked with lower odds of too little sleep.
How much sleep do teenagers need?
The American Academy of Sleep Medicine recommends 8 to 10 hours per 24 hours for teens aged 13 to 18, on a regular basis. Late phone use eats into that window from the bedtime side, because school start times fix the wake-up.
Does night mode or a blue light filter solve the problem?
The 2026 study did not test filters. It measured minutes of phone use, which can push bedtime later whatever the screen color. Moving the phone out of the bedroom addresses both the time and the light.
Sources
- Zhao Y, Hale L, Christakis DA. Evening Phone Use and Sleep Outcomes Among Youth. JAMA Pediatrics, 19 October 2026. doi:10.1001/jamapediatrics.2026.4902. https://pubmed.ncbi.nlm.nih.gov/42895708/
- HealthDay News, via Powers Health. Smartphones Are Wrecking Teens’ Sleep, Study Says. 21 October 2026. https://www.powershealth.org/about-us/newsroom/health-library/2026/10/21/smartphones-are-wrecking-teens-sleep-study-says
- Nagata JM, Kim KE, Leong AW, Christakis DA, Baker FC, Hale L. Smartphone Use on School Nights in the Adolescent Brain Cognitive Development Study. JAMA Pediatrics, 2026;180(8):908-911. doi:10.1001/jamapediatrics.2026.1707. https://pubmed.ncbi.nlm.nih.gov/42149585/
- FOX 5 New York. Teens spend nearly an hour on phones in late-night hours before school, study finds. 19 May 2026. https://www.fox5ny.com/news/teens-spend-nearly-hour-phones-late-night-hours-before-school-study-finds
- Bren Z, Tran KT, Visoki E, et al. Smartphone Acquisition and Use at Age 13 Years and Health Outcomes at Age 14 Years. JAMA Pediatrics, 2026;180(8):858-866. doi:10.1001/jamapediatrics.2026.2118. https://pubmed.ncbi.nlm.nih.gov/42258187/
- American Academy of Sleep Medicine. Recommended Amount of Sleep for Pediatric Populations (consensus statement). 2016. https://aasm.org/resources/pdf/pediatricsleepdurationconsensus.pdf
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