Children who use social media just three times a day are much more likely to have mental health issues, a study suggests.
Scientists analysed data from interviews with 13,000 teenagers that went to more than 1,000 schools across England.
University College London experts found rates of anxiety were 28 per cent higher in teenage girls who used social media more often.
Boys also suffered from scrolling through popular sites such as Facebook, Twitter and Instagram – but not by as much.
Researchers now say it’s unlikely flicking through social media sites directly harms mental health.
Instead, they believe spending hours on social media can leave girls vulnerable to cyber bullying, as well as causing a lack of sleep and exercise.
Other factors are thought to be behind the effects of social media on the mental health of boys.
Professor Russell Viner, lead researcher of the study, said: ‘Our results suggest that social media itself doesn’t cause harm.’
He added that, instead, ‘frequent use may disrupt activities that have a positive impact on mental health’.
Professor Viner said: ‘I think one of the conclusions is that social media does not displace physical activities in boys in the same way that it does in girls, which may be one of the reasons for this difference that we see.’
The teenagers were quizzed between 13 to 16 at three different time points – 2013, 2014 and 2015.
Very frequent social media use was defined as using networking sites, including WhatsApp and Snapchat, three or more times a day.
In the second year of the study, all of the participants completed a questionnaire which assessed psychological distress,
This term covered a range of different symptoms including sadness, anxiety and difficulty focusing.
Each of the teenagers were also quizzed about their sleep quality, physical activity and if they had been a victim of cyber bullying.
In the third and final year, all the participants were surveyed about their wellbeing, such as life satisfaction, happiness and anxiety.
Use of social media rocketed between 2013 and 2015, according to the findings in The Lancet Child and Adolescent Health journal.
Just 43 per cent of boys and 51 per cent of girls used social media multiple times a day at the beginning of the study.
However, the figures had jumped to 69 per cent and 75 per cent, respectively, by 2015, the researchers discovered.
Very frequent social media use was linked to greater psychological distress in both sexes.
In girls, the more often they accessed or checked social media, the greater their psychological distress.
Some 28 per cent of girls who frequently used social media were distressed in 2014, compared with 20 per cent of those using it weekly or less.
And girls who used social media very frequently in the first two years of the study had lower wellbeing by the end of the project.
Their life satisfaction and happiness was 14 and 20 per cent lower, on average. And their symptoms of anxiety increased by 28 per cent.
Sleep disruption and cyber bullying caused nearly 60 per cent of psychological distress and almost all of the effect on wellbeing in girls, the authors said.
Reduced physical activity also played a role but to a much lesser extent, according to the scientists.
The findings were not as significant in the boys. The three factors explained only 12 per cent of the impact of social media use on psychological distress.
The authors accepted that their study did not capture how much time in total was spent using social media, which may have impacted the findings.
Co-author Dr Dasha Nicholls said the differences uncovered could be down to girls having higher levels of anxiety to begin with.
She also suggested it ‘could simply be attributed to girls accessing social media more frequently than boys’.
‘Cyber bullying may be more prevalent among girls,’ Dr Nicholls said. ‘Or it may be more closely associated with stress in girls than in boys.
‘The results of our study make it all the more important to undertake further detailed studies of the mechanisms of social media effects by gender.’
Experts welcomed the study. Dr Ann DeSmet from Ghent University, Belgium, said the findings are ‘important’.
Experts said interventions that suggest cutting back on the amount of time spent on social media may not be effective.
Instead, youngsters should focus on spending more time exercising, socialising in real life and getting adequate shut-eye.
Solutions offered by the team include parents insisting their children leave their phones downstairs when they go to bed to ensure their sleep is not disrupted.
They should also monitor who their child is speaking to online to check for cyber-bullying, and make sure their child is staying active.
In the UK, more than 90 per cent of teenagers use the internet for making and talking to friends.
There is growing concern about how this impacts mental health, considering early adolescence is when mental illnesses tend to begin.