The research, carried out by Dieter Wolke from the University of Warwick, studied more than 4,000 children in the UK and US. The team regularly measured rates of maltreatment - assessed as physical, emotional, or sexual abuse or harsh discipline - and bullying - characterised as repetitive aggressive behaviour by someone in their peer group with more power - by interviewing the children and their parents. The researchers then assessed the children for mental health problems when they were 18-years-old.
In the UK group, maltreatment was linked to depression but this wasn’t the case in the US group. But bullying was linked to mental health problems for children in both groups.
The team worked out the odds of developing mental health problems linked to maltreatment and the odds linked to bullying. They discovered bullied children were around five times more likely to experience anxiety and nearly twice as likely to report depression and self-harm at age 18 than maltreated children.
It is difficult to say whether or not the team captured the true rates of maltreatment in the study since in many cases, they relied on parents admitting child abuse. If rates of maltreatment were missed then the findings linked to maltreatment may reflect an inaccurate picture.
But even if rates of maltreatment were missed, the findings linking bullying to mental health problems remain.
The team also looked at the relationship between bullying and mental health while taking into account other factors such as family hardship and the mental health of mothers. The harmful effects of bullying remained even when controlling for these other factors, again lending support to their conclusions.From www.shutterstock.com
But the investigators did not assess all key factors that could explain the link between bullying and mental health problems. Childhood speech and language problems, for example, which were not assessed, are known to be linked to peer bullying in childhood and anxiety disorders in adulthood.
A study carried out by Joe Beitchman and his team at the University of Toronto followed children for 14 years. They discovered that speech and language problems at the age of five were strongly linked to anxiety problems in young adulthood. The most common anxiety problem in adulthood was social anxiety disorder.
In my own clinical practice, I frequently treat people suffering from disabling social anxiety who have a history of bullying. Sometimes my clients have a history of maltreatment and bullying, but more often than not they have a history of bullying. For many people, bullying ruptures healthy self-esteem, replacing positive beliefs about oneself with beliefs linked to shame, disgust and criticism.
If a child is teased for an aspect of their appearance, they may go on to believe they look distorted and ugly. When they look in the mirror they may actually see an image of themselves encapsulating the names that bullies call them. They may develop body dysmorphic disorder, an anxiety disorder that causes people to have a distorted view of their appearance and to spend a lot of time worrying about it.
But more commonly, past bullying is linked to social anxiety disorder. People with social anxiety disorder are terrified of socialising with others, fearing harsh evaluation and rejection. They typically underachieve at school and at work and are at risk of depression and early death by suicide.
Social anxiety disorder typically starts around the time bullying starts in childhood. Many people with this disorder recover as adults when their bullying is re-visited in treatment. The therapist will help the client to transform the meaning of the bullying so that it is no longer seen as a sign of weakness but rather as evidence confirming the weakness of the bullies. Clients also learn to update their negative images with realistic images of how they really come across to other people.
In some ways knowing how bullying leads to poor mental health is less important than preventing bullying. Zero tolerance programmes are needed and government recommendations should be implemented in every school - and monitored.
For example, it would be helpful if, as part of the nationwide curriculum, students learned to spot the signs of bullying in themselves and others. Classroom discussions about the effects of bullying would help to raise awareness among children.
Children who are likely to bully need help to handle their difficult feelings and to learn positive communication skills. Their parents may need support too. Parenting classes may help or interventions that teach parents how to manage their own difficult feelings could be beneficial.
Schools should make it easy for kids to report bullying and to access immediate help. GPs should routinely ask about bullying when children visit the surgery. If teachers, health professionals, parents and children can work together to spot the signs and symptoms of bullying and stop it, there will be scope to prevent the linked mental health problems from developing.
Dr Jennifer Wild is a Senior Research Fellow in Clinical Psychology in the Department of Experimental Psychology at Oxford University. She is also a Consultant Clinical Psychologist.
Her research has covered post-traumatic stress disorder and trauma, and in relation to events such as the Chilean mining disaster, the Japanese tsunami, and the Costa Concordia shipwreck. She has also worked on anxiety, depression and how the brain forms memories.
Dr Wild has considerable broadcast experience, including appearances on BBC Breakfast,
Sky News and Today (BBC Radio 4). She is a regular contributor to BBC Radio 5 Live.