Attention deficit-hyperactivity disorder, a common childhood disorder, appears to result from a metabolic dysfunction in the brain, new research indicates.
The research may help resolve longstanding controversy over whether ADHD is primarily psychological or has a physical basis in the brain.The study shows that in at least one area - the way the brain processes a simple sugar that is the body's energy "currency" - there is such a physical basis.
Brain scans of adults who were hyperactive since childhood showed that their brains processed glucose more slowly than the brains of non-hyperactive adults, researchers with the federal National Institute of Mental Health report in Thursday's issue of the New England Journal of Medicine.
"The findings . . . represent a clear advance in our understanding of the biologic antecedents of hyperactivity," wrote Dr. Gabrielle Weiss of Montreal Children's Hospital.
Hyperactivity affects between 1 percent and 5 percent of children, depending on its definition; some experts say it can affect as many as 10 percent. Children tend to become fidgety or act out in inappropriate settings, such as the classroom, and consistently have difficulty concentrating and paying attention over long periods of time.
It affects boys much more often than girls, and it can continue into adolescence and even adulthood. Evidence suggests a hereditary component, since fathers and sons often exhibit indications of the disorder.
Paradoxically, the disorder typically is treated with mild stimulants, which seem to help in the control of symptoms but have no impact on the long-term course of the disorder.
Dr. Alan Zametkin and colleagues at NIMH found the brains of adults diagnosed as hyperactive tended to metabolize, or process, the sugar on average 8.1 percent more slowly than the brains of the non-hyperactive adults. Moreover, the greatest difference in metabolism was in those parts of the brain associated with attention and motor movement.