There’s been some discussion in recent years about how to conceptualize attention-deficit/hyperactivity disorder (ADHD), and what type of disorder it actually is. Neurobiological evidence in the last few years has suggested that ADHD does have roots in the brain—and a new study in Journal of the International Neuropsychological Society offers some more solid evidence that ADHD can be seen in the brain from an early age. How this type of evidence affects the discussion or informs treatment options, isn’t so clear, but it's still good to have, to understand more about how the disorder works in general.
The study, from Kennedy Krieger Institute, scanned the brains of 90 four- and five-year-olds, a little over half of whom were kids with ADHD who had never been on medication. Compared to controls, the participants with ADHD had reduced volume in the cerebral cortex (the outer layer of the brain), in areas in three of the four lobes of the brain. The team says the differences were mainly in regions known to be involved in cognitive and behavioral control—which children with ADHD are typically lower in. They were also linked to predictability of behavioral symptoms; in other words, the neurological differences in the kids with ADHD matched their parents’ reports of their symptoms.
"These findings confirm what parents have known for a while – even in very young children, ADHD is a real biological condition with pronounced physical and cognitive manifestations," said study author E. Mark Mahone.
It’s certainly not the first study to find neurological differences in the brains of people with ADHD. A study last year found that both children and adults had differences in volume in five different areas of the brain—and the differences in children’s brains were more obvious than adults’. Other studies have found altered white matter, the “highways” of projections that connect neurons to each other, in the brains of people with ADHD.
And the new research does suggest there may be fundamental changes in the brain that exist from an early age. This may not be too surprising, since behavioral symptoms generally have some sort of biological correlate; but it may help researchers understand how the disorder develops and changes, or evens out over time. The team behind the current study will follow the participants as they age to see just this.
"Our hope is that by following these children from early on in life, we will be able to determine which early brain and behavioral signs are most associated with later difficulties, or even better, which aspects of early development can predict better outcome and recovery from the condition," said Mahone. "By understanding the brains of children who grow into the disorder as well as those who grow out of it, we can begin to implement targeted, preventative interventions in young children with the goal of reducing adverse outcomes or even reversing the course of this condition."
Not every expert believes that “ADHD” is the best way to conceptualize the constellation of symptoms, or that it’s a single disorder at all. Those discussions are far from settled. But perhaps as more neurobehavioral research comes in, it will inform how clinicians, researchers, and the education system think about and treat the disorder, and people who have it.
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