Brain Scans Reveal ADHD Differences
Some Children with ADHD May Have Different Levels of Brain Chemicals
WebMD News Archive
Dec. 4, 2003 -- Children with attention deficit hyperactivity
disorder (ADHD) may actually have different levels of certain chemicals in the
brain than other children, a new study shows.
Using new imaging techniques, researchers found that children
with the hyperactive form of ADHD had 2 1-2 times more of a brain chemical
known as glutamate, which acts like a stimulant in the brain. In addition, the
brains of children with this subtype of ADHD also had lower than normal levels
of GABA, a chemical that has inhibitory properties in the brain.
Both of these chemicals are neurotransmitters that carry
signals to and from nerve cells in the brain. Researchers say these differences
may explain the behavior of children with poor impulse control.
"Glutamate is an excitatory amino acid that leads to easier
stimulation and excited neuronal pathways," says researcher Helen
Courvoisie, MD, assistant professor of child and adolescent psychiatry at Johns
Hopkins Medical Institutions in Baltimore. "GABA is an inhibitory
neurotransmitter and inhibits those pathways in the brain."
In addition to revealing differences in brain chemistry, the
study also showed that these gaps correlated to the children's scores on tests
of language, memory, sensory, and learning skills.
Courvoisie discussed the findings of the study Thursday at a
briefing on neurological disorders sponsored by the American Medical
Association in New York City. The study also appears in the December issue of
the Journal of Neuropsychiatry and Clinical Neurosciences.
The Brain and ADHD
Researchers stress this is only a preliminary finding and more
study is needed to confirm these results. But by better understanding the
workings of the brain in children with ADHD through studies like this, they may
be able to develop improved treatments. The findings may also eventually lead
to the discovery of a biomarker for ADHD that could be used in screening for
The study used a variation of MRI (magnetic resonance imaging)
to measure the levels of six chemicals in a small area in the frontal lobe of
the brain. This area is responsible for controlling several key functions
involved in ADHD, including impulse control, attention, movement, and