By PERRI KLASS, M.D.
Published: December 13, 2010
As recently as 2002, an international group of leading neuroscientists found it necessary to publish a statement arguing passionately that attention deficit hyperactivity disorder was a real condition
In the face of “overwhelming” scientific evidence, they complained, A.D.H.D. was regularly portrayed in the media as “myth, fraud or benign condition” — an artifact of too-strict teachers, perhaps, or too much television.
In recent years, it has been rarer to hear serious doubt that the disorder really exists, and the evidence explaining its neurocircuitry and genetics has become more convincing and more complex
Even so, I’ve lately read a number of articles and essays that use attention (or its lack) as a marker and a metaphor for something larger in society — for the multitasking, the electronic distractions, the sense that the nature of concentration may be changing, that people feel nibbled at, overscheduled, distracted, irritable.
But A.D.H.D. is not a metaphor. It is not the restlessness and rambunctiousness that happen when grade-schoolers are deprived of recess, or the distraction of socially minded teenagers in the smartphone era. Nor is it the reason your colleagues check their e-mail in meetings and even (spare me!) conversations.
“Attention is a really complex cognitive phenomenon that has a lot of pieces in it,” said Dr. David K. Urion of Harvard, who directs the learning disabilities and behavioral neurology program at Boston Children’s Hospital. “What we’re specifically talking about in kids with attention deficit is a problem compared to age- and gender-based peers in selective attention — what do you glom onto and what do you ignore?”
Moreover, the disorder occurs along a broad spectrum, from mild to extreme. Boys are more likely to be hyperactive and impulsive, girls to be inattentive. (One reason many girls don’t get an official diagnosis is that those with the inattentive form may be well behaved in school, but still unable to focus.)
“There’s a lot we still don’t know,” said Bruce F. Pennington, a professor of psychology at the University of Denver and an expert on the genetics and neuropsychology of attention disorders. “But we know enough to say it is a brain-based disorder, and we have some idea about which circuits are involved and which genes.”
Imaging studies of people with attention deficits have shown a consistent pattern of below-normal activity in the brain’s frontal lobes, where so-called executive function resides. And scientists are focusing on the pathways for dopamine and similar neurotransmitters active in the circuits that pass information to and from the frontal lobes.
Low levels of activity in specific circuits may help explain the seeming paradox of using stimulants like Ritalin to treat children who already seem overstimulated. In many children with A.D.H.D., these drugs can help the circuits function more normally.
“If you have a deficit in dopamine, it’s harder to concentrate on goal-oriented behavior,” Professor Pennington said. “The psychostimulants change the availability of dopamine in these same circuits.”
Although recent research has identified environmental factors that may increase the likelihood of developing the disorder, it is thought to have a stronger genetic component. Dr. Maximilian Muenke, chief of the medical genetics branch at the National Human Genome Research Institute, said that among identical twins, if one has A.D.H.D., the second has an 80 percent chance of having it as well. (Among fraternal twins, the comparable figure is 20 to 30 percent, the same as for any siblings.)
Dr. Muenke’s group published a paper last month identifying a gene, LPHN3, that is associated both with the disorder and with a favorable response to stimulants. But no one thinks that just one gene is responsible; just as attention is a complex phenomenon, so are the genetics of attention deficits.
When I asked Dr. Muenke whether genetic studies could someday play a role in treating the disorder, his reply was cautious. He spoke of eventually predicting which children will respond to specific medications, sparing families the frustration of switching from one medicine to another with no relief. He sounded more hopeful about the long-term prospects.
“I truly believe in the long run we will be able to develop personalized medicine for a child with A.D.H.D.,” he said, adding that when the specific underlying cause or causes are known, “this child will have a very specific treatment, whether this treatment is behavioral treatment alone or medication,” and the medication will be tailored to the child.
Perhaps eager to make clear that A.D.H.D. is far more than a metaphor for the distractions of modern life, scientists love to point out examples that date to well before the term was invented.
Dr. Urion invoked Sir George Frederick Still, the first British professor of pediatric medicine, who in 1902 described the syndrome precisely, speaking of a boy who was “unable to keep his attention even to a game for more than a very short time,” and as a result was “backward in school attainments, although in manner and ordinary conversation he appeared as bright and intelligent as any child could be.”
Dr. Muenke brought up “Der Struwwelpeter“ (“Slovenly Peter”), the 1845 children’s book by Heinrich Hoffmann, which contains the story of “Zappel-Philipp,” or “Fidgety Philip.” (One English translation was done by Mark Twain, that great chronicler of boys.)
The circumstances of modern life can give rise to the false belief that a culture full of electronics and multitasking imperatives creates the disorder. “People have this idea that we live in a world that gives people A.D.H.D.,” Dr. Urion said. Of course one shouldn’t drive and text at the same time, he continued, but for “a harbor pilot bringing a huge four-masted sailing vessel into Boston Harbor, paying attention was a good idea then, too.”