In youth with attention deficit hyperactivity disorder (ADHD), the brain matures in a normal pattern but is delayed three years in some regions, on average, compared to youth without the disorder, an imaging study by researchers at the National Institutes of Health’s (NIH) National Institute of Mental Health (NIMH) has revealed in a press release on November 12, 2007. The delay in ADHD was most prominent in regions at the front of the brain’s outer mantle (cortex), important for the ability to control thinking, attention and planning.  Otherwise, both groups showed a similar back-to-front wave of brain maturation with different areas peaking in thickness at different times.

“Finding a normal pattern of cortex maturation, albeit delayed, in children with ADHD should be reassuring to families and could help to explain why many youth eventually seem to grow out of the disorder,” explained Philip Shaw, M.D., NIMH Child Psychiatry Branch, who led research team.

The motor cortex emerged as the only area that matured faster than normal in the youth with ADHD, in contrast to the late-maturing frontal cortex areas that direct it. This mismatch might account for the restlessness and fidgety symptoms common among those with the disorder, the researchers suggested.

They 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.