Recent research suggests that stimulants can balance abnormal brain chemistries that cause attention deficit hyperactivity disorder in children.

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According to the National Institute of Mental Health, ADHD affects 3 to 5 percent of children in the United States. Children with ADHD have difficulty controlling their behavior or focusing their attention.

Researchers from North Shore-Long Island Jewish Health System in New Hyde Park, N.Y., said children who have ADHD display anatomical brain abnormalities beyond chemical imbalance. In another study, scientists found that stimulants, prescribed to balance brain chemistry, appear to normalize some of these brain irregularities.

The research was presented Monday at the annual meeting of the Radiological Society of North America in Chicago.

"We found abnormality of the fiber pathways in the frontal cortex, basal ganglia, brain stem and cerebellum," said Dr. Manzar Ashtari, who is the lead author of both studies. "These areas are involved in the processes that regulate attention, impulsive behavior, motor activity and inhibition -- the key symptoms in ADHD children."

Scientists compared 18 children with ADHD to 15 control children using diffusion tensor imaging to evaluate the brain's white-matter fiber development. They found differences in the fiber pathways that transmit and receive information among brain areas.

"Typically, ADHD is described as a chemical imbalance, but our research has shown that there may also be subtle anatomical differences in areas of the brain that are important in this disorder," said Dr. Sanjiv Kumra, another researcher in the study.

In the second study, the researchers found that children who had received stimulant treatment for ADHD had fewer white matter abnormalities than children who did not receive medication. The fiber pathways in the brains of children medicated for ADHD were more normalized than those who weren't medicated.

Most people diagnosed with ADHD in childhood continue to have problems in adolescence and adulthood. Ashtari said more studies with larger patient groups must be conducted before offering parents advice for diagnosis or treatment.