Study: Teens use cellphones for an hour a day at school
Social media apps are the main content. The effect of state laws governing phone use at school “remains to be seen,” a study author says.
University of Washington School of Medicine/UW Medicine
U.S. adolescents spend more than one hour per day on smartphones during school hours, with social media accounting for the largest share of use, according to research published Jan. 5, 2026, in JAMA. The findings have relevance for educators, parents and policymakers.
The study reflects the behavior of 640 adolescents ages 13-18 who were enrolled in the Adolescent Brain Cognitive Development Study. They and their parents had consented to have software placed on their Android cellphones that allowed use to be passively monitored. Usage was measured between September 2022 and May 2024.
Key findings:
- Adolescents spent an average of 1.16 hours per day on smartphones during school hours.
- Social media apps Instagram, TikTok and Snapchat accounted for most use, followed by YouTube and games.
- Older adolescents (16–18) and those from lower-income households showed higher smartphone use, compared to peers of the same age.
“These apps are designed to be addictive. They deprive students of the opportunity to be fully engaged in class and to hone their social skills with classmates and teachers,” said Dr. Dimitri Christakis, the paper’s senior author. He is a professor of pediatrics at the University of Washington School of Medicine and practices at Seattle Children's Hospital.
Based on a national sample of students, the results build on findings published last year in JAMA Pediatrics. That study had fewer participants but also included iPhone users.
At least 32 states and the District of Columbia require school districts to ban or restrict students’ use of cellphones in schools. The effect of those policies “remains to be seen,” Christakis said.
“To date they've been very poorly enforced, if at all. I think the U.S. has to recognize the generational implications of depriving children of opportunities to learn in school,” he added.
The paper’s lead author is Dr. Jason Nagata, an associate professor of pediatrics at the University of California San Francisco.
“This moves the conversation beyond anecdotes and self-reports to real-world behavior. Teens are not always accurate reporters of their own screen time. Objective smartphone data gives us a clearer picture of actual use,” Nagata said.
The research was supported by the National Institutes of Health (K08HL159350, R01MH135492, R01DA064134).
Related: Among U.S. adults, 71.3% supported the banning of smartphones in schools, according to a companion research letter published in JAMA Pediatrics. For that paper, the researchers analyzed a 2023 survey of 35,000 adults in 35 countries.
Journal
JAMA
Method of Research
Data/statistical analysis
Subject of Research
People
Article Title
Smartphone Use During School Hours by US Youth in the Adolescent Brain Cognitive Development Study
Article Publication Date
5-Jan-2026
COI Statement
Dr Nagata reported receiving grants from the National Institutes of Health (NIH) during the conduct of the study. Dr Hale reported receiving personal fees from the National Sleep Foundation for chairing the Screens and Sleep Consensus Panel and from the Children and Screens Institute for co-editing a handbook; receiving grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) and Della Pietra Family Foundation; and serving as an expert witness for social media litigation outside the submitted work. Dr Baker reported receiving grants from the NIH during the conduct of the study. Dr Christakis reported serving as an expert consultant in social media litigation for Motley Rice outside the submitted work. No other disclosures were reported.
Sleeping in on weekends may help boost teens’ mental health
Regular sleep is best, but catching up on weekends can lower risk of depression symptoms, UO research finds
University of Oregon
Sleeping in on the weekend to catch up on sleep lost during the week may be good for adolescents’ mental health, according to new research by the University of Oregon and the State University of New York Upstate Medical University.
The study found that a group of young people, age 16 to 24, who caught up on sleep on the weekend had a 41 percent lower risk for symptoms of depression than a group who didn’t.
The findings, published in the Journal of Affective Disorders, highlight the important link between sleep and mental health in adolescents, a population marked by sleep challenges and heightened risk for symptoms of depression. Yet that age group has rarely been included in studies of weekend catch-up sleep.
Eight to 10 hours a night is still best
The study provides the first glimpse into weekend catch-up sleep for typical U.S. adolescents. Previous studies focused on school-age teens in China and Korea.
It’s common for U.S. teens to rack up a sleep deficit during the week because of everything competing for their time and attention: school, social life, extracurricular activities, and often an after-school job.
“Sleep researchers and clinicians have long recommended that adolescents get eight to 10 hours of sleep at a regular time every day of the week, but that’s just not practical for a lot of adolescents, or people generally,” said Melynda Casement, a licensed psychologist, associate professor in the UO’s College of Arts and Sciences and director of the UO’s Sleep Lab. She co-authored the paper with Jason Carbone, assistant professor of public health and preventive medicine and of family medicine at the State University of New York Upstate Medical University.
Getting the recommended eight to 10 hours of sleep each night is still ideal, the researchers emphasize. But if that’s not possible, then sleeping in on weekends may help lower the risk of symptoms of depression.
“It’s normal for teens to be night owls, so let them catch up on sleep on weekends if they can’t get enough sleep during the week because that’s likely to be somewhat protective,” Casement said.
In the study, researchers analyzed data on 16- to 24-year-olds from the 2021-23 National Health and Nutrition Examination Survey. The young adults reported their bedtimes and wake-up times during the week and weekend, which researchers used to calculate their weekend catch-up sleep, the difference between the average sleep per weekend day and the average sleep per weekday.
Study participants also reported how they were feeling and were counted as having symptoms of depression when they reported feeling sad or depressed daily.
Sleep patterns change in adolescence
Sleep cycles, known as circadian rhythms, start shifting in adolescence, making it harder for most teens to fall asleep as early as they did when they were younger.
“Instead of being a morning lark you’re going to become more of a night owl,” Casement explained. “And sleep onset keeps progressively delaying in adolescence until age 18 to 20. After that, you start becoming more morning larkish again.”
The typical sleep cycle for teenagers is to fall asleep around 11 p.m. and wake at 8 a.m. That conflicts with early start times at many U.S. high schools. As a result, many sleep scientists and health care providers support the public health campaign to start schools later.
Depression is one of the leading causes of disability among 16- to 24-year-olds, Casement said. In this context, disability is defined broadly as impairment of daily functioning, such as calling in sick or being late to work.
“It makes that age range of particular interest in trying to understand risk factors for depression and how those might relate to delivery of interventions,” Casement said.
Journal
Journal of Affective Disorders
Article Title
Weekend catch-up sleep and depressive symptoms in late adolescence and young adulthood: Results from the National Health and Nutrition Examination Survey
Article Publication Date
1-Feb-2026
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