A new study found teens who spent more time on their phones before bed were more likely to use them again later that night.
Researchers tracked smartphone activity objectively using an app rather than relying on self-reported screen time.
The findings suggest cutting back on phone use before bedtime may help reduce overnight screen time.
For many teenagers, checking a phone before bed is part of the nightly routine. Whether it's scrolling social media, watching videos, texting friends, or playing games, those last few minutes of screen time can easily stretch longer than expected.
Now, new research suggests that what happens before bedtime may influence what happens after falling asleep, too.
Researchers found that when teens used their smartphones more than usual during the hour before bed, they were more likely to pick up their phones again later that same night. The study adds to researchers' understanding of how nighttime smartphone habits may develop and why late-night phone use can become a recurring pattern.
“On evenings when adolescents used their smartphone more before bed, they used it for a longer time later that night, potentially leading to later bedtimes and greater sleep disruption,” lead author Gina Marie Mathew said in a news release.
“Limiting smartphone use before bed may help reduce nighttime phone use and thereby improve sleep among teens.”
The study
The study included 229 adolescents from across the United States who owned or primarily used their own smartphones.
Participants first completed surveys about their backgrounds and sleep schedules before installing an app called RealityMeter, which objectively tracked their smartphone activity over an average of nearly 17 days.
Rather than asking teens to estimate their screen time, the researchers measured actual phone use. They focused on the hour leading up to each participant's typical bedtime and categorized activity into total smartphone use, social media use, and non-social media activities, such as messaging, gaming, or streaming videos.
The researchers then compared that pre-bedtime activity with smartphone use later in the night. Overnight use was defined as activity between midnight and 5 a.m. on school nights and between 1 a.m. and 6 a.m. on non-school nights.
They specifically examined whether teens spent at least 30 minutes using their phones during those overnight hours.
What the findings could mean
The results showed a clear pattern.
On evenings when teens spent at least 30 minutes using their phones before bed, they were more likely to spend at least 30 minutes using their phones later that same night compared with evenings when they spent less time on their devices before bed. The association was observed for overall smartphone use and for non-social media activities, while social media use showed a similar trend.
According to the researchers, this pattern suggests that smartphone use before bedtime may make additional phone use overnight more likely, increasing the opportunity for later bedtimes and interrupted sleep.
While the study did not test whether reducing bedtime phone use directly improves sleep, the researchers say limiting smartphone use before bed could be a practical strategy for helping reduce overnight phone activity and supporting healthier sleep habits.
“Using passively measured, objective smartphone data allowed us to examine these associations at the within-person, nightly level, providing a granular look at how pre-bedtime phone use relates to additional late-night use in adolescents’ daily lives,” Mathew said.