Conducting the largest imaging study of attention-deficit hyperactivity disorder to date, researchers have identified differences in five brain regions, suggesting that the condition should be treated like a brain disorder.
In a study published in The Lancet Psychiatry, Martine Hoogman and colleagues carried out the largest look at brain volumes of individuals diagnosed with ADHD, working with more than 3,200 people for the research. According to them, their findings may aid in improving the understanding of ADHD, challenging beliefs about the condition to do away with labels attached to it.
Associated by the study with delayed development in five regions of the brain, ADHD affects 5.3 percent or more than one out of every 20 children aged 18 years old and below, with two-thirds of children diagnosed with the condition still experiencing symptoms into adulthood.
ADHD And Brain Volumes
This is not the first time that brain volumes have been linked to ADHD but previous studies had small sample sizes that rendered results inconclusive. Nonetheless, the findings of previous studies identified areas within the basal ganglia - the brain region responsible for controlling cognition, voluntary movement, and emotion - as being involved in ADHD, with putamen and caudate regions being specifically observed as smaller in those with the condition.
For the current study, the researchers worked with 1,713 individuals with ADHD and 1,529 without, with ages ranging from 4 to 63 years old. All study subjects underwent MRI scans to measure overall brain volume as well as the size of seven of the brain regions believed to be linked to the condition: the hippocampus, amygdala, nucleus accumbens, putamen, caudate nucleus, thalamus, and pallidum.
Based on their findings, the researchers found that five of the seven brain regions were smaller in those diagnosed with ADHD. These brain regions were the hippocampus, amygdala, nucleus accumbens, putamen, and caudate nucleus.
Imaging ADHD In The Brain
"These differences are very small ... so the unprecedented size of our study was crucial to help identify these," said Hoogman, the study's lead author. Hoogman also added that similarities in brain volume differences were also observed in other psychiatric disorders, particularly major depressive disorder.
The putamen and caudate nucleus have been linked before to ADHD but it was only now that researchers were able to associate the hippocampus, amygdala, and nucleus accumbens conclusively to the condition.
According to them, the amygdala's connection to ADHD is through the brain region's role in emotion regulation while the nucleus accumbens is related to emotional and motivational problems with the condition because of the role it plays in reward processing. The hippocampus' role in ADHD is believed to have something to do with emotion and motivation as well.
Given the differences in brain structure they discovered, Hoogman and colleagues suggest that ADHD should be treated like a brain disorder, and not just some label for poor parenting or difficult children.
"This is definitely not the case," reiterated Hoogman.
To further observe how ADHD manifests throughout life, the researchers said longitudinal studies designed to track subjects from childhood into adulthood will be needed and will be an important next step in their work.