Self-harming among teenage girls has risen "rapidly" in recent years, according to new research.
Between 2011 and 2014 reports of self-harm among British girls aged between 13 and 16 rose by 68%, experts at the University of Manchester found.
An increase in common mental health disorders and the impact of digital media were suggested as possible reasons behind the rise.
Nav Kapur, professor of psychiatry and population health at the University of Manchester, said of the reasons behind the increase: "It could reflect better awareness or recording of self-harm in primary care. But it could also be a result of increasing stress and higher levels of psychological problems in young people.
"There is some evidence indicating that common mental health disorders are becoming more common within this age group.
"The internet and social media can be really helpful in preventing self-harm but could have negative effects too and this is a focus of significant research and activity."
The study, published in The British Medical Journal, found that between 2001 and 2014, 16,912 children and adolescents were identified as having self-harmed at least once. Of these, 73% were girls.
For girls, the rate of self-harm was 37.4 out of every 10,000 girls, compared to 12.3 per 10,000 boys.
For girls aged 13 to 16 the rate rose from 45.9 per 10,000 in 2011 to 77.0 per 10,000 in 2014.
In about 55% of cases of self-harm, no referral to mental health services was documented. The authors said that referral rates to psychiatric services were "low" which suggests "less severe cases or possible reflection of the challenges in accessing specialist services in a timely manner".
The authors also assessed risk of death by comparing 8,638 youngsters who had self-harmed to 170,274 children who had not. A total of 43 deaths occurred among young people in the self-harm cohort and 176 in the comparison group. Those who had self-harmed were nine times more likely to die unnaturally - including suicide and accidental death - compared to their peers, they calculated.
An NSPCC spokesman said: "These heartbreaking figures are sadly unsurprising because Childline hears from so many young people who hurt themselves.
"Self-harm can often be an expression of a deeper problem which is why early intervention services to support these children are vital."