Brain Matures a Few Years Late in ADHD, But Follows Normal Pattern
A study by the National Institute of Mental Health sheds some light on the brain development of youths suffering attention deficit hyperactivity disorder, also known as ADHD.
Akinso: A study by the National Institute of Mental Health sheds some light on the brain development of youths suffering attention deficit hyperactivity disorder, also known as ADHD. According to the study the ADHD brain matures in a normal pattern but that development is delayed by three years in some regions. The delay was most prominent in regions at the front of the brain's outer mantle, known as the cortex—the area responsible for the ability to control thinking, attention and planning. Dr. Philip Shaw, a researcher from the NIMH Child Psychiatry Branch, discusses the study.
Shaw: The current study, really ever since ADHD was first described, there's been a debate about whether it represents a delay in brain development or whether it's due to a complete deviation away from normal brain development. To address this question we looked at the cortex and we measured the thickness of the cortex across thousands of points in the brain in about 450 kids, some with ADHD some without. And we looked at how the cortex developed. What we found is that in all children the cortex starts off quite thin it then gets thicker. It reaches its peak thickness and then starts thinner throughout adolescence. And the big difference we find in the current study was between the ADHD kids and the kids who didn't have ADHD was in the age at which they reached this milestone of peak cortical thickness throughout the brain. So for healthy kids they sort of peak around age 7 or 8, whereas the ADHD kids there delayed and they reach their peak at about age 10.
Akinso: In both ADHD and control groups, sensory processing and motor control areas at the back and top of the brain peaked in thickness earlier in childhood, while the frontal cortex areas responsible for higher-order executive control functions peaked later, during the teen years. Dr. Shaw compared the pattern of brain development.
Shaw: So while there was delay the sequence or the order in which the different parts of the brain matured was very similar in both the kids with ADHD and those who didn't have it. So if ADHD was a complete deviation away from normal brain development you'd expect the sequence to be completely disrupted and it wasn't. So we think this is pretty strong evidence that ADHD is more of a delay in brain development.
Akinso: Researchers also noted that the delayed pattern of maturation observed in ADHD is the opposite of that seen in other developmental brain disorders like autism, in which the volume of brain structures peak at a much earlier-than normal age. Dr. Shaw said the findings support the theory that ADHD results from a delay in cortex maturation. He added that he hopes to find genetic underpinnings of delay and ways of boosting processes of recovery from the disorder. This is Wally Akinso at the National Institutes of Health Bethesda, Maryland.
About This Audio Report
Reporter: Wally Akinso
Sound Bite: Dr. Philip Shaw
Topic: Attention Deficit Hyperactivity Disorder