Girls’ much-higher rate of depression than boys is closely linked to the greater time they spend on social media, and online bullying and poor sleep are the main culprits for their low mood, new research reveals.

As many as three-quarters of 14-year-old girls who suffer from depression also have low self-esteem, are unhappy with how they look and sleep for seven hours or less each night, the study found.

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“Girls, it seems, are struggling with these aspects of their lives more than boys, in some cases considerably so,” said Prof Yvonne Kelly, from University College London, who led the team behind the findings.

The results prompted renewed concern about the rapidly accumulating evidence that many more girls and young women exhibit a range of mental health problems than boys and young men, and about the damage these can cause, including self-harm and suicidal thoughts.

The study is based on interviews with almost 11,000 14-year-olds who are taking part in the Millennium Cohort Study, a major research project into children’s lives.

It found that many girls spend far more time using social media than boys, and also that they are much more likely to display signs of depression linked to their interaction on platforms such as Instagram, WhatsApp and Facebook.

It found that two in five girls are on social media at least three hours a day compared to a fifth of their male peers. While one in 10 boys do not use social media at all, only 4% of girls said the same.

“The link between social media use and depressive symptoms was stronger for girls compared with boys. For girls, greater daily hours of social media use corresponded to a stepwise increase in depressive symptoms,” explained Kelly.

For example, while 7.5% of 14-year-old girls and 4.3% of 14-year-old boys have been the victim of online harassment, 35.6% of girls who are depressed have experienced that – double the 17.4% of boys who have done so. Among teenagers who had perpetrated online bullying, 32.8% of girls and 7.9% of boys were depressed.

That pattern of stark gender differences was repeated when young people were quizzed about other key aspects of their feelings and behaviour, Kelly’s team found.

Social media is also closely associated with poor sleeping habits, especially among 14-year-olds showing clinical signs of depression. While just 5.4% of girls and 2.7% of boys overall said they slept for seven hours or less, 48.4% of girls with low mood and 19.8% of such boys said the same. Half of depressed girls and a quarter of depressed boys said that they suffer from disrupted sleep “most of the time”.

The authors say the sleep disruption is due to young people staying up late to use social media and being woken up by alerts coming in to their phones beside their beds. Their findings are published on Friday in EClinicalMedicine, a journal published by the Lancet.

“Inevitably there is the chicken and egg question, as to whether more dissatisfied children, who to begin with are less pleased with their body shape and have fewer friends then spend more time on social media. Nonetheless, it is likely that excessive use of social media does lead to poorer confidence and mental health,” said Prof Stephen Scott, the director of the national academy for parenting research at the institute of psychiatry, psychology and neuroscience at King’s College London.

Prof Sir Simon Wessely, an ex-president of the Royal College of Psychiatrists, said the researchers “still cannot definitely say that social media usage causes poor mental health, although the evidence is starting to point in that direction”.

Government ministers and Simon Stevens, the chief executive of NHS England, have called on social media companies to do much more to limit the amount of time young people spend using their platforms. Stevens has suggested taxing companies to help the NHS cover the costs of treating soaring numbers of under-18s suffering problems such as anxiety, depression, eating disorders and psychosis, which Theresa May has made a personal priority.

Anne Longfield, the children’s commissioner for England, has warned that even some children as young as nine “are becoming almost addicted to ‘likes’ as a form of social validation that makes them happy, and many are increasingly anxious about their online image and ‘keeping up appearances’.

“Their use of platforms like Instagram and Snapchat can also undermine children’s view of themselves by making them feel inferior to the people they follow,” she added.

Barbara Keeley, the shadow minister for mental health, said social media firms should be forced to adopt a new duty of care to protect young users.

But Dr Nihara Krause, a consultant clinical psychologist who specialises in teenagers’ mental wellbeing, cautioned against heaping too much blame on social media for the huge recent rise in mental ill-health among under-18s. “Depression and all mental ill-health conditions arise due to a range of complex factors, usually a biological, psychological and social mix,” she said.

An NHS England spokesperson said: “These findings add to the growing evidence base and show precisely why the concerns that we and others have raised about the potential harmful links between social media and young people’s mental health need to be taken seriously.

“Everyone must start taking responsibility, including social media giants, to help young people develop and maintain good mental health, rather than let problems build up to the point that they need specialist help from the NHS.”

‘It really affected the way I looked at my own body’

Facebook Twitter Pinterest Shannon McLaughlin Photograph: Shannon McLaughlin

Shannon McLaughlin, 18, from Blackburn, has opened up about how social media has harmed her mental health.

“Since being diagnosed with depression and anxiety in my early teens, my mental health has definitely been affected by social media. The sad truth is that people mostly share the positive things about life on social media, without showing the negatives. This really affected me when I was struggling with my mental health and would constantly scroll through Facebook and Instagram. Seeing that everyone was happy and enjoying life made me feel so much worse. In fact, it made me feel like I was doing something wrong. Why was I feeling so different to everyone else?

“It not only affected how I was feeling about myself mentally, but also physically. I was constantly confronted by women with unattainably skinny bodies who were praised for the way they looked. Even though I was a size 10, it really affected the way I looked at my own body. This was only made worse by the abundance of diet fixes and skinny culture promoted by ‘influencers’, whose posts are broadcast to thousands of people every day.”

McLaughlin does volunteer work, including putting on blind football events. She is travelling to Germany on Friday to work on one such programme and, while there, will research the provision of services for blind people in that country, as well as how those same services can possibly be improved in the UK.

About two years ago, she began volunteering with the National Citizen Service. “When I was 16, I decided it was important for me to invest time in new friends and people that made me feel positive in real life. That’s when I decided to go on National Citizen Service. NCS was life-changing for me. It made me connect with real people, build my confidence and feel less alone. It’s so important for young people to make real connections without hiding behind a text message or a happy social media post.

“It’s so easy to forget the importance of real connections when we constantly have hundreds of people that we’re trying to impress at our fingertips. I think it’s important for young people to look up from their phones and focus more on the world around them, and the amazing connections that they can make there.”