Four times as many girls than boys end up in A&E after trying to harm themselves, a study suggests.
Abusive relationships and bullying were a major factor
Paul Clarke, a nurse at Springfield University Hospital, examined A&E records at two major hospitals in London over an 18 month period.
He found that staff treated 164 boys and girls between the ages of 10 and 15 after they had harmed themselves.
His findings were presented at the Royal College of Nursing research conference in Cambridge.
Most of those who had self-harmed had drunk excessive amounts of alcohol while almost one in three had overdosed on paracetamol.
Two out of three youngsters said they had difficult or abusive relationships, in most cases with their parents.
Almost half said bullying was their biggest problem, with girls much more likely to say they had been bullied.
Mr Clarke found that 59% of those identified by the study were discharged without any specialised follow up.
One in eight of all of those identified by the study went on to self-harm again.
Mr Clarke said the study findings provided a tiny snapshot of what is actually happening.
"Self-harm is quite prevalent," he told BBC News Online. "We have to remember that most cases of self-harm don't end up in a hospital admission.
"For instance, in the community habitual cutting is much more prevalent."
Mr Clarke said hospitals needed to do more to ensure young people who tried to hurt themselves received the follow-up care they need.
"We need to think about developing other services that are more sensitive to their needs," he said.
A national inquiry into self-harm is being launched next week. It will examine why so many young people are harming themselves and what can be done to help them.
"At least one in 10 young people are self-harming. That means probably two people in a classroom," said Catherine McLoughlin, who is involved in the inquiry.
"We need to do something about it."