Study Shows That Brain Will Develop Slowly in ADHD Cases

A new study released by the National Institutes of Health's National Institute of Mental Health (NIMH) shows that brain development in children with Attention Deficit Hyperactivity Disorder is delayed compared with children without ADHD. The delay may be up to three years in the cortex, or outer mantle, of the brain. As the child matures past childhood and into adolescence, however, a normal pattern of growth is shown.

The NIMH study concentrated on images of the brain that hadn't previously been scanned for the thickness of the cortex. It is the cortex of the brain that is responsible for attention and planning skills, and the actual control of one's thinking.

When comparing the cortex thickness in children with ADHD, maximum thickness of certain areas is achieved around age ten, whereas in children without the disorder, maximum thickness in the same areas is seen around age seven. This comparison of thickness is measured in 40,000 sites within the brain.

Previous to this latest study by the NIMH, most researchers were looking at growth and development in the lobes of the brain, rather than the cortex. A new imaging technique had made it possible for scientists and researchers to see the cortex and the many specific sites around the brain in order to compare the thickness and thinness in normal brains and those afflicted with ADHD and other disorders.

The head of the research team at the NIMH's Child Psychiatry department, Doctor Philip Shaw, commented in the NIH press release announcing the findings, "If you're just looking at the lobes, you have only four measures instead of 40,000. You don't pick up the focal, regional changes where this delay is most marked."

It seems that the areas and circuits in the brain that coordinate sensory information with the control functions shows the most significant delay in those children and teens with ADHD. The control functions are housed in the frontal cortex, whereas the sensory processors and motor functioning controls are in the top and back of the brain.

Another result of the new imaging study is that children and teens with ADHD show signs of faster development in the motor cortex, which the researchers point out makes sense as it is that area that would produce physical activity. The common symptoms of ADHD is restlessness or fidgeting, which could be explained by the overdeveloped motor cortex not being kept under control by the frontal control cortex.

Another interesting finding is that the delay in development in the frontal cortex in ADHD-afflicted children is the exact opposite of what happens in the brains in children with autism.

The NIMH researchers plan on continuing studies in this vein, and hope to find the genetic causes of the delay. Dr. Shaw adds that the imaging is not yet ready to diagnose the condition, as the delays are only noticeable when compared across many brain images.

Source: National Institute of Mental Health