A major new study on ADHD has found that the condition is linked with the delayed development of five regions of the brain and as a result, it should be considered a disorder of the brain.

According to Dutch researchers, these findings are important to dispel the myth that ADHD is simply a label for difficult children or the result of poor parenting.

ADHD (Attention Deficit Hyperactivity Disorder) affects around 5% of people under the age of 18 and the majority of these will continue to experience symptoms in adulthood.

Symptoms can include poor concentration, an inability to complete tasks, getting distracted easily, restlessness, not being able to remain seated and excessive talking.

This study is the largest imaging study of ADHD to date. It involved carrying out MRI scans of 3,242 people, just over half of whom had been diagnosed with ADHD.

The MRI scans measured the participants' overall brain volume, as well as the size of seven different regions of the brain that were thought to be linked to ADHD.

The study found that the overall volume of the brain was smaller in people with ADHD. It also found that the volume of five specific regions was smaller - the caudate nucleus, putamen, nucleus accumbens, amygdala and hippocampus -irrespective of whether the participants were taking medication for the condition or not.

"These differences are very small - in the range of a few percent - so the unprecedented size of our study was crucial to help identify these. Similar differences in brain volume are also seen in other psychiatric disorders, especially major depressive disorder," explained the study's lead author, Dr Martine Hoogman, of the Radboud University Medical Center in the Netherlands.

Dr Hoogamn emphasised that these findings ‘confirm that people with ADHD have differences in their brain structure', which suggests a disorder of the brain.

"We hope that this will help to reduce stigma that ADHD is ‘just a label' for difficult children or caused by poor parenting. This is definitely not the case, and we hope that this work will contribute to a better understanding of the disorder," she added.

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