Full Breakdown
Smartphones Delay Teen Sleep, Study Finds
By Drooid · · How we work
Study Findings on Evening Phone Use
Researchers analyzed data from 425 adolescents (average age ? 15) who are part of the NIH-funded Adolescent Brain Cognitive Development Study. Wearable fitness trackers recorded sleep patterns while a validated app logged smartphone activity. On nights when teens used their phones longer than their personal average after 10 p.m., they fell asleep about 64 minutes later and obtained roughly 20 minutes less total sleep. Phone use in the 15 minutes before bedtime was also linked to more frequent awakenings during the first half-hour of sleep. A dose-response pattern emerged: each additional minute of phone use past 10 p.m. further delayed sleep onset and reduced sleep duration.
Quantitative Results
- Participants contributed nearly 7,600 nights of data.
- Average nightly screen time was almost four hours, including about 40 minutes after 10 p.m.
- Girls logged more overall screen time; boys showed slightly higher late-night use.
- The shift in wake-up time was smaller than the delay in sleep onset, narrowing the “sleep opportunity window.”
Expert Interpretation
“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,” — Daniel Bigman, a child and adolescent psychiatrist and sleep medicine physician at Northwell Health
“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,” — Daniel Bigman, a child and adolescent psychiatrist and sleep medicine physician at Northwell Health
“What we’ve been saying for years, and what the totality of research supports, is that teens should not have phones in their bedrooms, because it interferes with sleep, which is fundamental for optimal functioning,” — Lauren Hale
Dr. Daniel Bigman, a child and adolescent psychiatrist at Northwell Health, emphasized that the combination of visual stimulation, notifications, and interactive engagement keeps the brain alert when it should be winding down. He noted that fragmented sleep can impair attention, mood and impulse control. Lauren Hale, a professor at Stony Brook Medicine and co-author of the study, highlighted that removing phones from bedrooms eliminates a major source of sleep interference and restores time for activities such as reading, sports or social interaction.
Guidance for Parents and Teens
The study’s authors recommend limiting smartphone use after 10 p.m. and turning devices off at least an hour before bedtime. Practical steps include charging phones outside the bedroom, using “Do Not Disturb” or “Sleep” modes, and substituting screen time with low-stimulus activities like reading a hard-copy book, listening to music, or doing relaxation exercises. Bigman cautioned against using phone removal as punishment; instead, he urged families to establish consistent, screen-free bedtime routines to protect sleep health.