Children who are bullied by their peers suffer worse mental health problems in the long term than those who have been maltreated by adults, new findings suggest.

UK researchers looked at over 4,000 people taking part in a UK study of parents and children, and more than 1,200 people taking part in a similar US study.

With the UK study, maltreatment between the ages of eight weeks and eight years was assessed, along with bullying at the ages of eight, 10 and 13. The mental health of the participants was checked at the age of 18.

The US study looked at reports of maltreatment and bullying between the ages of nine and 16, and the mental health of the participants between the ages of 19 and 25 years.

The researchers found that those who were bullied by their peers during childhood were almost five times more likely to suffer with anxiety at the age of 18 compared to those who were maltreated by adults.

Bullied children were also almost twice as likely to self-harm and suffer with depression later on, compared with maltreated children.

The results stood even when other influencing factors were taken into account, such as the mental health of the children's mothers and family hardship.

"The mental health outcomes we were looking for included anxiety, depression or suicidal tendencies. Our results showed those who were bullied were more likely to suffer from mental health problems than those who were maltreated. Being both bullied and maltreated also increased the risk of overall mental health problems, anxiety and depression in both groups," explained lead researcher, Prof Dieter Wolke, of the University of Warwick.

He noted that until now, governments have tended to focus their resources on family maltreatment rather than bullying. However, with one-third of children worldwide experiencing bullying, ‘more needs to be done to address this imbalance'.

"Being bullied is not a harmless rite of passage or an inevitable part of growing up. It has serious long-term consequences. It is important for schools, health services and other agencies to work together to reduce bullying and the adverse effects related to it," Prof Wolke added.

Details of these findings are published in the journal, The Lancet Psychiatry.