Teenagers using social media for more than three hours a day are more likely to go to bed after 23:00 and wake during the night, UK research suggests.
This affects one in three teens – with one in five spending five hours or more on apps like Instagram, WhatsApp and Facebook every day, the study said.
The University of Glasgow researchers said 13 to 15 year-olds may be delaying bedtime by being on their phones.
Psychiatrists say screens should be avoided in the hour before bed.
But the study, of 12,000 teenagers, recognised that getting them off their phones could be "especially challenging" because it was a time of growing independence, when keeping in touch with friends was important.
Teenagers who were very high social-media users (five hours or more per day) were around 70% more likely than average users (one to three hours) to fall asleep late on school nights and after midnight on other days.
The study adds weight to the theory that time spent by teenagers on social media is reducing the time they spend sleeping – and lack of sleep can have an impact on mental health, weight and performance at school.
How long do teenagers spend on social media?
|Hours per day||% of boys||% of girls||% of both|
|less than one hour||43.8||22.8||33.7|
|between one and three hours||32.1||31.1||31.6|
|from three to five hours||10.4||17.7||13.9|
|more than five hours||13.7||28.4||20.8|
Sleep is already in short supply at this age due to hormone changes making many teenagers want to go to sleep later and wake up later.
For the study, in BMJ Open, data was gathered from a representative sample of UK adolescents from 2015 who took part in the Millennium Cohort Study.
They were asked how much time they spent on social networking, messaging sites or apps on a typical school day and at weekends, and quizzed on their sleep habits.
One third said they used social media for less than an hour a day while the average was between one and three hours. These groups were least likely to fall asleep late.
Girls were twice as likely as boys to spend more than five hours on social media – and girls also had more disrupted sleep.
'Don't want to miss out'
Dr Holly Scott, from the school of psychology at Glasgow University, said the findings couldn't prove that high social media use caused disrupted sleep, but it appeared to be a "powerful competitor for sleep".
"Teenagers may be lying awRead More – Source