Study reveals brain differences in those with ADHD

Student raising handPeople with attention deficit hyperactivity disorder — especially children — have smaller brain volume than those who don't have ADHD, according to a recent study published in The Lancet Psychiatry.

This confirms that ADHD should be considered a brain disorder, according to the study titled “Subcortical brain volume differences in participants with attention deficit hyperactivity disorder in children and adults: a cross-sectional mega-analysis.”

“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,” said lead author Dr. Martine Hoogman, of Radboud University Medical Center in Nijmegen, The Netherlands. “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.”

ADHD affects more than one in 20 children younger than 18, and two-thirds of those diagnosed continue to experience symptoms as adults, according to a press release on the study. Symptoms include inattention and/or hyperactivity and acting impulsively.

The study is the largest to look at the brain volumes of people with ADHD and involved more than 3,200 participants — 1,713 with ADHD and 1,529 without. All participants had MRI scans to measure their overall brain volume and the size of seven regions of the brain thought to be linked to ADHD.

The study found that overall brain volume and the volume in five of the regions were smaller in people with ADHD. The areas of the brain affected include the caudate nucleus, putamen, nucleus accumbens, amygdala and hippocampus.

“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,” Hoogman said. “Similar differences in brain volume are also seen in other psychiatric disorders, especially major depressive disorder.”

The differences observed were most prominent in the brains of children with ADHD but less obvious in adults. Researchers proposed that delays in the development of several brain regions are characteristic of ADHD.

The researchers hypothesize that the amygdala is associated with ADHD through its role in regulating emotion, and the nucleus accumbens with the motivation and emotional problems through its role in reward processing. The hippocampus’s role in the disorder might act through its involvement in motivation and emotion.

The different volumes of the brain regions were present whether or not the participants took medication, suggesting the differences were not a result of psychostimulants— medication used to treat ADHD.

According to the authors, the next study should track people with ADHD from childhood to adulthood to see how the brain differences change over time.

For a story on Tactics for the ADHD homework wars click here.

By Betsy Stein