MRI scans of more than 3,200 subjects have confirmed a delay in the development of five brain regions in people with attention deficit hyperactivity disorder (ADHD), according to an international study published online February 15 in Lancet Psychiatry.
In the largest imaging study of ADHD to date, according to a statement from the journal, the greatest differences in brain development were found in children rather than adults. The researchers examined the brain structure of 1,713 people diagnosed with ADHD and 1,529 healthy control subjects between the ages of 4 and 63 years.
MRI scans were performed on all 3,242 participants to measure their overall brain volume and the size of seven brain regions thought to be associated with ADHD: the pallidum, thalamus, caudate nucleus, putamen, nucleus accumbens, amygdala, and hippocampus. The researchers also noted whether subjects with ADHD had ever taken psychostimulant medication such as Ritalin.
Overall brain volume and five of the regional volumes were smaller in people with ADHD, the group found. The volume differences were seen in the caudate nucleus, putamen, nucleus accumbens, amygdala, and hippocampus.
Similar differences in brain volume have been seen in those with other psychiatric disorders, especially major depressive disorder, noted lead author Dr. Martine Hoogman from Radboud University Medical Center in Nijmegen, the Netherlands.
At the time of the scans, 455 people with ADHD were receiving psychostimulant medication and 637 had taken the medication during their lifetime. The different volumes of the five brain regions involved in ADHD were present regardless of the use of medication.
In addition, the differences in brain volume were greater in children than adults. Based on the findings, the researchers suggested that ADHD is a disorder of the brain, and that developmental delays in several brain regions are characteristic of ADHD.
"The results from our study confirm that people with ADHD have differences in their brain structure and therefore suggest that ADHD is a disorder of the brain," Hoogman said in the statement. "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."
