The number of schoolgirls at risk of emotional problems has risen sharply, an English study in the Journal of Adolescent Mental Health suggests.
Scientists analysed questionnaires completed by 1,600 pupils aged 11-13 in 2009, comparing them with similar surveys conducted five years later.
They were “surprised” by a 7% spike in girls reporting emotional issues while boys’ answers remained fairly stable.
Charities are concerned pressures are particularly affecting girls.
Scientists found that social, peer and behavioural problems remained relatively constant for boys and girls across the five years.
But the rise in emotional issues reported by girls suggested they faced unique pressures, the researchers suggested.
They said reasons behind this could include a drive to achieve unrealistic body images perpetuated by social media and an increasing sexualisation of young women.
Funding cuts to mental health services might also be to blame, they suggested.
“In a climate of limited resources, it is also possible teachers may focus more on behavioural and conduct issues as these tend to disrupt classrooms,” researcher Dr Helen Sharpe, of University College London, told the BBC.
To help overcome this, researchers suggest staff should be given the right resources to look out for emotional problems.
And they argue mental health services should be more widely available.
Sarah Brennan, of the charity YoungMinds, said:”This research is shocking further concrete evidence of the serious and worsening state of children and young people’s mental health in this country.
“Young people tell us they feel enormous pressures today ranging from bullying, the 24/7 online environment and sexual pressures to issues around body image, school stress and family breakdown.
“YoungMinds is concerned that these are affecting girls in particular.”
In the online questionnaire, children were asked how strongly they agreed with a series of statements that are clinically validated to assess the risks of developing a range of mental health issues.
The sample in 2009 was tailored to match the demographics of children who filled in the survey in 2014.
The last comprehensive national survey of children’s mental health was undertaken by the Office for National Statistics more than a decade ago.
The Royal College of Psychiatrists says there is now an urgent need to conduct another one to gather accurate estimates of mental health problems and plan services accordingly.