Late-Night Smartphone Use Linked to Poorer Sleep Among Teens, Columbia Nursing Study Finds
New Columbia University School of Nursing-led research published in Journal of the American Medical Association Pediatrics offers insight into how late-night smartphone use may affect teen sleep.
After analyzing more than 7,500 nights of passively tracked smartphone activity and Fitbit-measured sleep from 425 U.S. teenagers from the National Institutes of Health-funded Adolescent Brain Cognitive Development (ABCD) study, researchers found that on nights when adolescents used their phones more than usual after 10 p.m., they fell asleep 65 minutes later and slept about 20 minutes less.
In more detail, each additional 30 minutes of phone use after 10 p.m. beyond a teen’s usual amount was associated with falling asleep about 26 minutes later, waking up about 11 minutes later, and getting about 13 minutes less sleep.
Teens woke up later on heavy-use nights, but not late enough to make up for the delayed bedtime, so total sleep shrank. The later in the evening phone use happened, the stronger the link to lost sleep.
Phone use in the final minutes before falling asleep tells a different story: teens who used their phones in the last five minutes before falling asleep spent more time awake during the first half hour after sleep onset. This 30-minute period is the window in which the brain normally settles into deep, slow-wave sleep, which supports next-day alertness, mood, and memory.
Evening phone use was mostly social media (YouTube, TikTok, Snapchat, Instagram). Teens in the study averaged nearly four hours of phone use a day, including about 40 minutes after 10 p.m.
The study, “Evening Phone Use and Sleep Outcomes Among Youth,“ was published on October 19, 2026.
Informing Family Habits and Future Approaches to Teen Sleep
The findings point to practical targets for families and researchers designing future intervention studies: limiting phone use after 10 p.m. and keeping the phone out of the final minutes before sleep.
“When a teen used their phone more than usual late at night, they tended to fall asleep later and get less sleep, and phone use right up to the moment of falling asleep was linked to more wakefulness early in the night,” said Yihong Zhao, PhD, lead author and professor at Columbia Nursing and Columbia University Data Science Institute.
“The study is observational, so we cannot conclude that phone use causes sleep changes. However, these findings suggest that the timing of phone use, not just the amount, should be an important part of the conversation about teen sleep. This matters because sufficient sleep during adolescence is essential.”
Other study authors include Lauren Hale, PhD, Stony Brook University, and Dimitri A. Christakis, MD, Seattle Children’s Research Institute.