Neuroradiologists from the Johns Hopkins University School of Medicine investigated the GABAergic component of ADHD using magnetic resonance spectroscopy to measure GABA concentration in somatosensory and motor cortices. Children (age range, 8-12 years) in a control group (n=19) were compared with an ADHD group of 13 children (11 boys and 2 girls) with a mean age of 10.2 years (range, 8.2-12.5 years). Children with IQ scores below 80 were excluded. Seven of 13 children with ADHD had received stimulant medication up to a day before the testing. In both medicated and unmedicated children, GABA concentration was reduced in children with ADHD compared with controls. This finding is concordant with known deficits in intracortical inhibition in ADHD and suggests a GABAergic deficit in ADHD. 
COMMENT. Deficit in behavioral inhibition is considered a basis for the symptoms of ADHD . Reduced GABA concentration in the cortex of both medicated and unmedicated children with ADHD is considered strong evidence for a GABAergic deficit in ADHD. Also, see GABA-ergic dysfunction in Tourette syndrome. (Pediatr Neurol Briefs 2012 July;26(7):54).