Girls were more likely to admit to self-harming than boys
A third of UK girls aged 11 to 19 have tried to harm themselves, a survey for a mental healthcare provider suggests.
More than half of the 800 young people said they knew someone who had self-harmed - either through cutting, burning or punching themselves.
The main reason given was feeling depressed, with the results among boys being slightly lower at 22%.
Mental health charities said the figures were "worrying" and adolescents needed better access to treatment.
The survey showed that 73% of young people who self-harmed admitted to cutting, 48% to punching themselves, 14% to burning and 10% to self-poisoning.
Of those who admitted to self-harm, 43% said they did it because they were depressed, 17% because they were angry, 10% because of relationship problems and 10% because they were stressed.
Dr David Kingsley, consultant psychiatrist at Cheadle Royal Hospital run by Affinity Healthcare - a mental healthcare provider for the NHS who commissioned the research - said professionals felt it was an increasing problem.
"One in three girls is an extraordinary figure - I was stunned by it.
"A study recently suggested three biggest causes were family problems, problems with friends and problems at school."
He said parents and teachers should be vigilant for young people who were withdrawn, struggling emotionally, or feeling low.
"We need to ask ourselves what it is about modern living that is causing such stress for our youngsters."
He said people often kept it secret from friends and family which stopped them getting help and sometimes young people were put off because they had a negative reaction when they confided in someone.
Marjorie Wallace, chief executive of the mental health charity Sane, said the findings were very troubling.
"Evidence from our own helpline suggests there is a growing epidemic of self-harm amongst our young, who are using ever more extreme ways to find release from their mental turmoil.
"It is an addictive and desperate way of dealing with the stresses of growing up.
"It is essential that the rising number of young people who self-harm are helped to stop before it develops into what may become a life-long illness."
She said any child suspected of self-harming needs to be identified early and treatment and counselling made available immediately.
Sarah Brennan, acting chief executive of Young Minds, said: "Parents often feel disempowered when they discover their child is self harming.
"Raising awareness to parents and those working in young people services will ensure parents have someone informed to turn to should their child be self harming."