From supercharged kindergartners to unfocused teenagers, attention deficit/hyperactivity disorder (ADHD) is one of the most controversial diagnoses of a childhood illness. Although some people don't think that ADHD is based in biology, a new study shows a strong link between ADHD and activity in part of the brain. What's more, when some kids with ADHD take medication, their brain activity begins to look like that of other kids.
The past few decades have seen a steady rise in the number of ADHD cases diagnosed in the United States. About 6% of all school-age children show the telltale signs of distractibility, impulsivity, and hyperactivity. Some kids inherit a predisposition to the condition, but for the most part researchers don't know what causes ADHD. Earlier, studies revealed that kids with ADHD have a shortage of a chemical messenger called dopamine in a part of the brain known as the striatum, which controls movement and some cognitive skills.
To spot which brain regions play a role in ADHD, neuroscientist Martin Teicher and colleagues at the McLean Hospital in Belmont, Massachusetts, and Harvard Medical School in Boston developed a more sophisticated analysis technique for functional magnetic resonance imaging. They imaged the brains of 11 boys with ADHD and six without. In boys with ADHD, the researchers report in the April Nature Medicine, a part of the striatum called the putamen was much less active. Furthermore, putamen activity correlated with ADHD symptoms: the more severe the case, the lower the putamen activity.
The researchers then gave some of the boys with ADHD Ritalin, the standard medication, and it eased their behavioral symptoms. Although it didn't detectably change the brain activity of some boys, Ritalin did boost putamen activity to almost normal levels in boys with the most severe symptoms of ADHD.
The study is the first to link medication to a change in brain activity in kids with ADHD, says clinical psychologist Stephen Hinshaw of the University of California, Berkeley. Because not all boys responded the same, according to the brain scan, this sort of technique may pave the way for a more reliable diagnosis of subtypes of ADHD, he says.