A third of schoolgirls with mental health problems have self-harmed or attempted suicide, rising to more than half of sixth-form girls, new research has revealed.
Data published by NHS Digital found 31.2% of girls aged 11 to 16 and 52.7% aged 17 to 19 had self-harmed or attempted suicide. This compared to 4% and 11.7% respectively in girls without a mental disorder.
The data, published as part of the Mental Health of Children and Young People in England report, also showed children and young people with mental health problems were more likely to spend long periods of time on social media.
A third of girls and nearly a quarter of boys with mental health disorders were found to spend more than four hours a day on social media. This compared to 12% of other children.
Nearly one in four (23.9%) 17 to 19-year-old girls had a mental health disorder compared to 14.4% of schoolgirls aged 11 to 16.
Children aged 11 to 19 with mental health problems were also more likely to compare themselves to others, spend more time on social media than they mean to, said they could not be honest about their feelings online and admitted that likes, shares and comments impacted their mood.
But Agenda, the alliance for women and girls at risk, warned the worrying figures could not blamed solely on body image and social media.
Chief executive Jemima Olchawski said the sexualisation of girls and "alarming" levels of sexual violence they experience was a key part of the problem.
Females aged 17 to 19 were more than twice as likely as boys to have a mental disorder. Find out more in our newest #MentalHealth of Children and Young People in England, 2017 report: https://t.co/uLsN7d0riypic.twitter.com/TyhOMExyxl
— NHS Digital (@NHSDigital) November 22, 2018
She added: "This serious and accelerating deterioration in young women and girls' mental health should concern us all.
"It is not enough to blame body image and social media. While they are rightly cited as possible explanations, they are not the full story.
"The sexualisation of girls, the pressures they face around sex, and particularly the alarming levels of sexual and other forms of violence they experience, must be a key part of the conversation."
She called for new investment to support girls, specifically to help them combat the impact of violence and abuse.
She said: "It is vital we see investment in mental health support that takes into account girls' needs and experiences, including the impact of violence and abuse, in both schools and the community to ensure they get the support they need, when they need it."
The survey was carried out for NHS Digital by NatCen Social Research, the Office for National Statistics and Youthinmind, and was funded by the Department of Health and Social Care.
1 in 8 children and young people aged between 5 and 19 has a mental disorder, the first major review of child #mentalhealth in England in 13 years has found. Read our full response to the findings here: https://t.co/fLwoy3qh0spic.twitter.com/uLjOmQhXsI
— SANE (@CharitySANE) November 22, 2018
Researchers collected data on 9,117 children through a combination of speaking to them, their parents or teachers.
It also found 5.5% of two to four-year-olds had a mental disorder, the equivalent of one in every 18 preschoolers.
Child and adolescent psychiatrist Professor Tamsin Ford warned that if mental health disorders are not treated, they can lead to problems for the child's whole life.
The Exeter University professor added: "Their health is poorer, their education outcomes are poorer, their health both physical and mental in adulthood is poorer, their life chances are seriously compromised."
The rate of mental health problems rises to more than one in 10 when children get to school age, with 11.2% of five to 15-year-olds affected.
This has risen from 9.7% in 1999 and 10.1% in 2004.
An increase in the number of young people affected by mental health issues has been driven by a rise in emotional disorders such as anxiety and depression, the report said.
These rose from 3.9% in 2004 to 5.8% in 2017.
The Royal College of Psychiatrists branded the new data a "harrowing picture" and called for the Government to increase its target of children being treated for mental health problems from a third to 70%.
Its child and adolescent faculty vice-chair Dr Jon Goldin said: "These figures paint a predictably harrowing picture of young people's mental health.
"What makes matters worse is that we know that the services designed to treat these issues are still underfunded and under resourced."
A Government spokeswoman said children's mental health was a "key priority" with an extra £2 billion a year promised.
She added: "This report shows exactly why it's so important we are ensuring 70,000 more children a year have access to specialist mental health care by 2020/21.
"And we're going further, piloting a four-week waiting time standard for treatment, training a brand new dedicated mental health workforce for schools across the country, and teaching pupils what good mental and physical health looks like through our new subjects of relationships and health education."