Spending three or more hours a day on social media is associated with poor sleep patterns, such as falling asleep after 11 pm on school nights and waking during the night, among UK teens, suggests research published in the online journal BMJ Open.
The findings "provide rigorous and meaningful evidence to inform practice and policy to support healthy adolescent sleep and social media use," say the researchers.
There is growing concern about the possible impact of screen time, and specifically social media use, on the mental health and wellbeing of young people. But there is little clear evidence to inform policy and clinical practice in this area.
To address this knowledge gap, the researchers set out to generate a typical profile of social media use and sleep patterns among UK teens.
They analysed data for 11,872 adolescents (aged 13-15) from the UK Millennium Cohort Study. This has been tracking the health of a large nationally representative sample of people born between 2000 and 2002.
Participants reported how much time they spent on social media to include social networking or messaging sites or Apps, such as Facebook, Twitter, and WhatsApp on a typical weekday.
They also reported typical sleep habits, including what time they fell asleep and woke up on both school days and free days; how long it took them to fall asleep; and any difficulties they had falling back asleep after waking during the night.
Just over a third (33.7%) of the teens said they spent less than 1 hour a day on social media so were classed as low users, while just under a third (31.6%) said they spent 1 to 3 hours a day on it, and were classed as average users.
Of the remainder, just under 14% were high users (3 to 5 hours a day) and around one in five (just under 21%) were very high users (more than 5 hours a day).
After taking account of family background as well as physical and psychological health, the researchers found that heavier social media use was generally associated with poorer sleep patterns.
Very high social media users were roughly 70% more likely to fall asleep after 11 pm on school days and after midnight on free days than were average users.
Both high and very high social media users were also more likely to say they woke later (after 8 am) on school days than average users, and very high users were more likely to say they had trouble getting back to sleep after waking during the night.
But low social media users were least likely to fall asleep late and wake up late, lending weight to the idea that social media displaces sleep. This is a particular concern on school days, as late bedtimes then "predict poorer academic and emotional outcomes," note the authors.
Girls tended to spend more time on social media than boys and reported poorer sleep quality.
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This is an observational study, and as such, can't establish cause. What's more, measures were based on self-report and duration of social media use only, rather than content or context, so may not have been completely accurate.
The researchers also acknowledge that heavy use of social media and difficulties falling asleep may reflect underlying health issues, as teens with poorer wellbeing may spend more time on social media and also experience sleep problems.
Nevertheless, they point out that this is a large, nationally representative study, which took account of a wide range of influential factors, and as such, "provides robust evidence on associations between social media use and sleep outcomes."
Future research should aim to build "a more nuanced, holistic understanding of adolescent social media use and sleep," they say.
And they call for approaches that help young people "to balance online social interactions with an appropriate sleep schedule that allows sufficient sleep on school nights, with benefits for health and educational outcomes."