A study published in “The Lancet Psychiatry” has linked attention-deficit hyperactivity disorder (ADHD) with brain development delays. This is the largest study surrounding ADHD to date, with over 3,200 subjects participating in the study.
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The participants ranged from four to 63 years old. About 1,700 of them had been diagnosed with ADHD and the other 1,500 were people who were not diagnosed with ADHD.
According to the Centers for Disease Control and Prevention, those who are diagnosed with ADHD must “show a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with function or development.”
In the inattention category, the CDC lists symptoms such as inability to pay close attention to detail, appearing not to listen when directly spoken to and trouble with organization.
Symptoms of hyperactivity and impulsivity can include fidgeting, getting up and leaving a seat when staying put is expected and talking excessively.
Previous research has found that areas in the basal ganglia are associated with those who have ADHD, which includes both the caudate and putamen regions.
Each of the participants had an MRI scan which measured overall brain volume and the specific size of seven regions of the brain thought to also be associated with ADHD, including the palladium, thalamus, caudate, putamen nucleus accumbent, amygdala and hippocampus.
Results showed that those with ADHD had smaller overall brain volume when compared to those participants without. Also, the size of five of the regions (caudate, putamen, nucleus accumbent, amygdala and hippocampus) were smaller in those with ADHD.
While previous research had already associated the caudate and putamen regions with ADHD, the amygdala, nucleus accumbens and hippocampus were conclusively linked to ADHD in this study.
Martine Hoogman, from Radboud University Medical Center in The Netherlands, said that the differences were small, within a few percent of each other.
“Similar differences in brain volume are also seen in other psychiatric disorders, especially major depressive disorder,” Hoogman said.
According to the research the differences were more observable in children with ADHD.
Hoogman said that the results confirm that those with ADHD do have a difference in brain structure, and that would suggest that ADHD is a disorder of the brain itself.
“We hope that this will help to reduce stigma that ADHD is ‘just a label’ for difficult children or caused by poor parenting,” Hoogman said. “This is definitely not the case, and we hope that this work will contribute to a better understanding of the disorder.”
