Being bullied could shrink the brain and lead to heightened risk of anxiety, a study has found.

Scientists claim it is the first time they have found changes in the size of the brain of victims of chronic bullying, compared to those who were not bullied.

These changes, the researchers said, can impact a person's behaviours including emotional processing, motivation, learning and attention later in life.

One in five children has been, or is being, bullied, according to statistics from the National Bullying Prevention Center in the US.

Surveys in the UK have shown half of primary school pupils and one in 10 secondary school pupils in England experience daily bullying.

Being bullied could shrink the brain, leading to heightened risk of anxiety, a study has found

Psychologists at King's College London conducted the study by analysing brain scans of more than 682 young people from across Europe.

The team, led by Dr Erin Burke Quinlan, used questionnaires to assess the mental health of the participants, who were aged between 14 and 19.

More than 30 of the youngsters had been chronically bullied, and their brain scans were compared with those who had not been bullied.

Bullying was linked to shrinking of brain size and a higher risk of anxiety at age 19, the findings, published in Molecular Psychiatry, show.

The parts of the brain affected are called the caudate and putamen.

The caudate plays a crucial role in how the brain learns, storing memories and using them to influence actions and decisions taken in the future.

The putamen, closely linked with the caudate, is involved with movements and learning. Alterations of the activity of the putamen have been associated with worse cognitive performance.

Previous studies have found a link between bullying and mental health issues, but these findings shed light on specifically why.

The authors said: 'Importantly, these findings were unique to peer victimization and not other types of stress or comorbid depression.

'Together, these results are, to our knowledge, the first to identify a possible mechanism by which adolescent peer victimization impacts the development of anxiety in young adults.'

Dr Burke Quinlan said: 'Although not classically considered relevant to anxiety, the importance of structural changes in the putamen and caudate to the development of anxiety most likely lies in their contribution to related behaviors such as reward sensitivity, motivation, conditioning, attention, and emotional processing.'

People who are bullied are two to three times more likely to develop an anxiety disorder, the authors said, highlighting the importance of prevention.

Previously research has found links between bullying and a higher risk of mental health problems during childhood, such as depression and an increased risk for suicide.