Study Links ADHD to Neurological Disorder, Not Behavioral Issues

ADHD A'Brain Disorder, Not Just Bad Behaviour Study

The worldwide team of researchers measured the differences in the brain structure of 1,713 people with a diagnosis of ADHD and 1,529 without, all aged between four and 63-years-old.

The volume overall was smaller in people diagnosed with ADHD, as were five of the brain regions, the team said.

The first author, geneticist Martine Hoogman of Radboud University in the Netherlands, said the amygdala "is a structure that is not so well known to be implicated in ADHD".

The findings are published this week in the medical journal 'The Lancet Psychiatry.' Specifically, the brains studied of ADHD patients have smaller amygdala and hippocampi, which would affect impulse control. The study project had been funded by the National Institutes of Health (NIS). The researchers also looked at the effect of age, gender, medication and other psychiatric disorders.

Previous studies which associated changes in brain volume with ADHD had been too small to be conclusive, the team said.

The affected regions include the amygdala, which is involved in the regulation of emotion.

"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", she said. Its ADHD project was four times the size of the previously largest study and was conducted at 23 locations in nine countries by 80 researchers, primarily psychiatrists and neuroscientists. Hoogman also added that similarities in brain volume differences were also observed in other psychiatric disorders, particularly major depressive disorder.

The study hopes to create more empathy for children with ADHD.

"We hope that this will help reduce stigma that ADHD is "just a label" for hard children or caused by poor parenting", said the study's leader author, Martine Hoogman of Radboud University Medical Center in the Netherlands, in a statement reported by AFP. "This is definitely not the case, and we hope that this work will contribute to a better understanding of the disorder".

The researchers also took into account whether the participants were taking, or had ever taken, medication to treat ADHD (such as Ritalin), but this appeared to have no effect on the findings.

"The reliability of ADHD research has not been great, because of [small] sample sizes", said Jonathan Posner, who did not take part in the study but who does pediatric brain imaging research at Columbia University Medical School. What they discovered was that the brains of those with attention and hyperactivity deficit disorder had 5 areas of the brain that were underdeveloped, when compared with the normal population.

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