One in ten teenage girls self-harm each year and the problem is far more widespread than was previously thought, shows the largest-ever study of self-harm amongst 15 and 16 year olds in England.
In a survey of more than 6,000 15 and 16-year-old school pupils, researchers found that girls are four times more likely to have engaged in deliberate self-harm compared to boys, with 11 per cent of girls and 3 per cent of boys reporting that they had self-harmed within the last year.
Previous estimates for the amount self-harm in the country were based on the 25,000 'presentations' at hospitals in England and Wales each year that are the result of deliberate self-poisoning or self-injury amongst teenagers.
However, research by academics from the universities of Bath and Oxford has found that only 13 per cent of self-harming incidents reported by the pupils had resulted in a hospital visit.
Although self-poisoning is the most common form of self-harm reported in hospitals, the study revealed that self-cutting was the more prevalent form of self-harm (64.5 per cent), followed by self-poisoning through overdose (31 per cent).
"The study shows that deliberate self-harm is common amongst teenagers in England, especially in girls who are four times more likely to self-harm than boys," said Dr Karen Rodham from the Department of Psychology at the University of Bath.
"Until now, most studies of deliberate self-harm in adolescents in the UK have been based on the cases that reach hospital.
"We have found that the true extent of self-harm in England is significantly wider than that."
Professor Keith Hawton from the Centre for Suicide Research at the University of Oxford, who directed the project, said: "This study provides more information about why young people engage in deliberate self-harm and helps us to recognise those at risk, to develop explanatory models and to design effective prevention programmes.
"In many cases, self-harming behaviour represents a transient period of distress, but for others it is an important indicator of mental health problems and a risk of suicide.
"It is important that we develop effective school-based initiatives that help tackle what has become a most pressing health issue for teenagers."
The research, which was carried out with Samaritans, has been published in the new book, By their own young hand, which includes practical advice for teachers on how to detect young people at risk - based on the evidence collected by the academics.
The book also suggests advice on coping with the aftermath of self-harm or attempted suicide in schools, and advice on designing training courses for teachers.
The research took place in 41 schools in Oxfordshire, Northamptonshire and Birmingham in 2000 and 2001.
Pupils were asked to complete a 30 minute questionnaire which explored issues surrounding self-harm and suicidal thinking - together with other personal factors such as depression, anxiety, impulsivity and self-esteem.
Those who reported self-harm were asked to provide a description of the act, its motivation and its consequences.
"The reasons why boys and girls decide to self-harm are varied but the most frequent motive expressed by both males and females was as a means of coping with distress," said Dr Rodham.
For both sexes there was an incremental increase in deliberate self-harm with increased consumption of cigarettes or alcohol, and all categories of drug use.
Self-harm was more common in pupils who had been bullied and was strongly associated with physical and sexual abuse in both sexes.
Also, pupils of either sex who had recently been worried about their sexual orientation had relatively higher rates of self-harm.
The majority of those who said they self-harmed said that it was an impulsive act rather than something they had thought about for a long time.
Almost half of those who cut themselves, and over a third who took overdoses, said that they had thought about harming themselves for less than an hour beforehand.
This means that there is often little time for intervention once thoughts of self-harm have been fully formulated.
Of those with a history of deliberate self-harm, 20 per cent reported that no one knew about it and 40 per cent of those who reported thinking about self-harm had not talked to anyone about it or tried to get help.
The vast majority of pupils said that their friends were the people they felt that they could talk to about things that bothered them and those who had self-harmed most often turned to their friends.
"This responsibility places a great burden on adolescents to support their peers, yet most adolescents have not in any way been coached in how best to do this," said Professor Hawton.
"Attention to this aspect of support for adolescents should be an essential part of mental health education in schools, and it is great to see the development of the wellness programmes currently being trialled in some schools.
"Whilst effort to encourage adolescents to seek help through friends, family, help lines and clinical services are very relevant, prevention should be focused on reducing the problems that lead to thoughts of self-harm.
"This is where school-based initiatives can make the most important contribution to this important aspect of mental health."
The research was funded by a £242,000 grant from the Community Fund.
For broadcast interviews contact Professor Keith Hawton on 01865 226258.
For other enquiries, please contact Andrew McLaughlin in the University of bath Press Office on +44 (0)1225 386 883 or +44(0)7966 341 357.
By their own young hand - deliberate self-harm and suicidal ideas in adolescents is written by Keith Hawton & Karen Rodham, with Emma Evans, and is published by Jessica Kingsley Publishers (ISBN 1 84310 230 7, 264pp, pb £17.99).
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Dr Rodham's web page
Professor Hawton's web page
Department of Psychology