Professor Philip Shaw describes a study in which the brains of children with ADHD tend to mature at a slower rate than a control group.

Here at the Child Psychiatry branch at NIH, we’ve been looking at kids as they grow up with ADHD. So we see the kids roughly by the age of 8, or 9, or 10, and then we see them every two years, and whenever we asses them clinically we also get a brain scan. From this brain scan, we use some sophisticated computer techniques to extract the cortex; the cortex is the gray matter or the outer mantle of the brain. We measure its thickness at thousands of points across the entire brain. Then we can, from that data, chart how the cortex grows over time and for all children, such as kids with ADHD and typically developing children, it’s the same general pattern. The cortex starts off relatively thin, it gets thicker with age, it then peaks and then it gets thinner throughout adolescence. One useful index of how the brain is maturing is the age at which each cortical point reaches its peak thickness. So that’s what we were looking at as a wave of maturation; at what age did every cortical point reach its peak thickness, and you can map that across the brain. So we looked at that in about 220 kids with ADHD and compared it with 220 kids who don’t have ADHD who are typically developing. And what you find is that both sets of kids showed the same general pattern of brain development. The brain or the cortex matures in the same sequence. The back parts of the brain (the posterior parts of the brain), which carry some of the most basic perceptual functions like seeing and hearing, they tend to mature early. Then the frontal parts of the brain which support the most complex of functions tend to mature quite late. But how the kids differed was the kids with ADHD, generally speaking, were delayed in reaching this milestone of brain development or brain maturation, and the delay was roughly about 3 years in order. But it varied a little bit throughout the brain, and the part that was most delayed was at the front and the side of the brain; the dorsolateral prefrontal cortex, and this part of the brain we think is particularly important for the very highest level of control of attention.

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