Image caption Being picked on at school can have serious consequences in the teenage years

Children bullied during their early years are up to three times more likely to self harm than their classmates when they reach adolescence, a study suggests.

It found that half of 12-year-olds who harm themselves were frequently bullied.

The researchers are calling for more effective programmes to prevent bullying in schools.

The study is published in the British Medical Journal .

The research, from King's College London, also showed that victimised children with mental health problems were at greater risk of self-harming in later life.

In their paper the authors suggest that efforts should focus on improving the ways in which children cope with emotional distress.

"Bullying by peers is a major problem during the early school years," they said.

Frequent victimisation by peers increased the risk of self harm. King's College London study

"This study found that before 12 years of age a small proportion of children frequently exposed to this form of victimisation already deliberately harmed themselves and in some cases attempted to take their own lives.

"Frequent victimisation by peers increased the risk of self harm."

Persisting problems

The researchers also raised fears over the long-term implications of bullying which, they said, could result in psychological issues, serious injury or death.

"This study adds to the growing literature showing that bullying during the early years of school can have extremely detrimental consequences for some children by the time they reach adolescence," they wrote.

"This finding is even more concerning given that studies have suggested that early patterns of self harm can persist through adolescence into adulthood and increase the risk of later psychological problems."

The authors looked at more than 1,000 pairs of twins - born between 1994-1995 in England and Wales - at five, seven, 10 and 12 years old.

The children were assessed on the risks of self-harming in the six months prior to their twelfth birthdays.

Data from 2,141 participants showed that 237 children were victims of frequent bullying and, of that number, 18 (around 8%) self harmed.

This involved cutting or biting arms, pulling out clumps of hair, a child banging its head against walls or attempting suicide.

Of 1,904 children who were not bullied, 44 (2%) self harmed.

It also showed bullied children who had family members who had either attempted or committed suicide were more likely to self harm than others.

"Although only a small proportion of bullied children in this sample engaged in self harm, this is clearly too many and victims need to be provided with alternative coping strategies from a young age," the authors said.