Children with attention deficit hyperactivity disorder (ADHD) display anatomical brain abnormalities beyond chemical imbalance, according to research presented at the annual meeting of the Radiological Society of North America (RSNA). Stimulant medications prescribed to balance brain chemistry appear to normalize some of these brain irregularities, a second study reported.
http://www.sciencedaily.com/releases/2004/11/041129103049.htm