ADHD, or attention deficit hyperactivity disorder, is a developmental mental disorder that affects three to five percent of school age children.
According to the ]]>National Institutes of Health (NIH)]]>, “ADHD is a problem with inattentiveness, over-activity, impulsiveness, or a combination. For these problems to be diagnosed as ADHD, they must be out of the normal range for the child's age and development.” As part of the ADHD diagnosis, children must have six inattention symptoms, or six hyperactivity-impulsiveness symptoms. The cause of ADHD is unknown, though previous neuroimaging studies showed that children with ADHD may have different levels of serotonin, adrenaline and dopamine. However, recent research by the NIH suggests that ADHD is due to different brain structure developments.
In November 2007, the ]]>NIH]]> released their findings from a neuroimaging study. 446 participants, 223 of whom had ADHD, underwent brain scans. Researchers found that children with ADHD had slower developing brains, but only in certain areas. While sensory processing and motor control areas in the brain developed equally in both test groups, the frontal cortex development in children with ADHD was delayed. Development of the frontal cortex peaks during the teen years, according to the NIH, while development of the sensory processing and motor control area peaks during childhood.
The difference in development of the frontal cortex, which controls thinking, attention and planning, is not permanent. The NIH study showed that thickness of the cortex peaked on average at age 10.5 for children with ADHD; children who did not have ADHD had cortex thickness peaking on average at age 7.5. “Otherwise, both groups showed a similar back-to-front wave of brain maturation with different areas peaking in thickness at different times,” according to the NIH. The conclusion of the study was that even though children with ADHD had a delayed maturation of the frontal cortex, they caught up developmentally within three years.