WEDNESDAY, Oct. 21, 2026 (HealthDay News) — Smartphones are costing teenagers a good night’s sleep, a new study says.
Teens who use their phones late into the evening suffer from delays in falling asleep, shorter total sleep time, and sleep that’s more restless and broken, researchers reported Oct. 19 in JAMA Pediatrics.
“These findings suggest that reducing evening smartphone use, particularly after 10 p.m. and immediately before bedtime, may help improve sleep health in adolescents,” concluded a team led by Dr. Dimitri Christakis, a professor of general pediatrics at Seattle Children’s Research Institute.
For the study, researchers analyzed data on 425 kids with an average age of nearly 15 who were participating in an ongoing study of adolescent brain development. They gathered nearly 7,600 nights of data from the participants.
Results showed that on nights when teens used their phone longer than their personal average after 10 p.m., they slept an average 20 minutes less and fell asleep more than an hour (64 minutes) later.
Teens glued to their phones also were more likely to wake up again within a half-hour after they nodded off, researchers said.
There also was a dose effect, in that every extra minute of smartphone use past 10 p.m. above a teen’s own average added to later sleep onset and reduced total sleep time, the study said.
"In short, the study did show that it kind of pushes bedtime later, and it makes it harder to transition into a stable sleep," said Dr. Daniel Bigman, a child and adolescent psychiatrist and sleep medicine physician at Northwell Health in New York City, who reviewed the findings.
There are several likely reasons for this, he said in a news release.
"For one, any kind of activity before sleep time will displace your sleep. Teens can simply stay up later when they use their phones,” Bigman said.
But beyond that, phones can stimulate the brain in ways that could affect sleep, he said.
“Things like social media, videos, texting, notification, lights, these are all signals to the brain that get transmitted through our senses, eyes and ears, and it tells our brain to stay alert when it really should be winding down,” Bigman said.
“And then there's light. We know that light is a main sensory component when it comes to managing the sleep-wake cycle,” he added. “That light in itself can shift our sleep cycle."
This is one of the first studies to indicate what might be considered an appropriate cutoff time for teens’ phone use, Bigman said.
“It showed that use after 10 p.m. was linked to later sleep difficulties or total sleep time,” he said. “Even phone use right before bedtime, meaning five to 15 minutes before falling asleep, also was linked to more wakefulness that occurs during the night.”
Teens in particular need a good night’s sleep, Bigman said.
“We know that sleep fragmentation in children or adolescents, specifically in teenagers, leads to worse attention, poor concentration, poor sleep performance, more irritability and emotional reactivity,” Bigman said. “It can induce higher stress levels, more anxiety and even contribute to a depressed mood. And in addition, it can cause daytime sleepiness, lower motivation and even difficulty with impulse control or decision making.”
However, he said parents shouldn’t threaten to take away a teen’s phone, but instead should encourage replacing their use “with other types of winding-down activities that may not be as stimulating,” including “reading, music, relaxation exercises and stretching” that “we know promote a sleep environment.”
More information
The Sleep Foundation has more on light-emitting devices and sleep.
SOURCES: JAMA Pediatrics, Oct. 19, 2026; Dr. Daniel Bigman, child and adolescent psychiatrist and sleep medicine physician, Northwell Health, New York City
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