ADHD Experts Fear Brain-Growth Study Being Misconstrued
Educators sat up and took notice last month when researchers published the results of a groundbreaking brain-imaging study suggesting that attention deficit hyperactivity disorder stems from delayed brain maturation.
National education and advocacy groups put the news on their Web sites, and The New York Times featured findings from that and another study in a front-page article. Implicit in some of the coverage was the hopeful idea that many—even most—children eventually grow out of the disorder.
But that’s not exactly true, according to the researcher who led the brain-imaging study and other experts.
“I think there’s been a bit of overinterpreting going on,” said Russell A. Barkley, a clinical professor of psychiatry at the Medical University of South Carolina, in Charleston, an ADHD expert who was not connected with the brain-imaging study. His own research, based on longitudinal surveys and behavioral observations, has long suggested that only 14 percent to 35 percent of children with ADHD fully overcome the symptoms by age 27.
Experts fear that potential misinformation about the disorder will cause clinicians, parents, and educators to take a wait-and-see approach with students who have ADHD, rather than tackle the problem head-on.
“I just hope people don’t say these kids don’t need treatment or that they don’t need medicine, because then our kids will develop gaps in learning,” said Chris A. Zeigler Dendy, a former special educator and school psychologist who is the author of books on teaching students with ADHD. All three of her adult children have a form of the condition.
Nationwide, an estimated 3 percent to 5 percent of children are diagnosed with ADHD, which is often marked by difficulties in paying attention, planning, organizing, and controlling activity levels, among other areas. Experts say the condition actually comes in three forms: a hyperactive type, marked by children who are restless or fidgety; an inattentive form, which produces children who are more daydreamers than behavior problems; or a combination of the two.
Debates and confusion have raged around ADHD ever since it surged to national prominence in the early 1990s. Scholars argue over whether ADHD stems from developmental delays or lasting brain differences. Some critics still question whether it even exists.
And parents and educators sometimes clash over whether children should take powerful stimulants, such as those known by the brand names Adderall and Ritalin, to improve their behavior in the classroom; be treated with therapy; receive classroom accommodations; or all of the above.
A recent study found that some parts of the brains of children with ADHD, mainly areas of the prefrontal cortex important in controlling thinking, attention, and planning, mature later. Light blue and light purple shading above show when various regions of the cortex reached their peak thickness. Areas in black, dark blue, and dark purple were not studied.
For the new study, which was published online Nov. 16 in the Proceedings of the National Academy of Sciences, researchers from the National Institute of Mental Health, in Bethesda, Md., used magnetic-resonance-imaging technology to study the brains of 446 children—half of whom had been diagnosed with the disorder—over 15 years.
In particular, the scientists measured the thickness of the cortex, which is the brain’s outer layer of gray matter, in different regions of the brain and at different points in time as the children grew up. The cortex thickens as the brain develops; after reaching its peak thickness, it thins as the brain matures.
What the NIMH researchers found was that in the brains of children and adolescents with the disorder, more than half of the cortex did not reach peak thickness until around age 10½, nearly three years later than was the case in normally developing children.
The lag was most pronounced in the prefrontal areas of the brain, which control many cognitive functions that are implicated in ADHD. They include: impulse control; organizational and attention skills; working memory, which is the ability to hold information and manipulate it at the same time; and some higher-order motor functions.
Similarities vs. Differences
Despite those delays, the study found, brain development in the ADHD children followed the same basic sequence as in the more typical children. The finding throws some cold water on the idea that children with ADHD have some sort of stable brain abnormality.
Where the NIMH study makes its mark, though, is in documenting biological evidence of developmental delays in the brain’s cortex. Previous brain-scan studies missed those differences because researchers used fewer subjects or fewer measuring points. The researchers draw on more than 40,000 measurements taken over the course of the study.
“This wasn’t showing that brains catch up and become completely normalized,” said Dr. Philip Shaw, the lead researcher, referring to the new findings. “There are still lots of very important differences.”
Studies that measure brain volume or function, for instance, still turn up differences between the brains of children with and without ADHD. “But they’re all pointing to the same brain region as being different,” added Dr. Shaw, a research psychiatrist in the child-psychiatry branch at the NIMH.
“Two-thirds of children will still have a lot of symptoms as adults,” he stressed in an interview, although earlier reports of his research said he put that estimate closer to one-fourth.
Some coverage of the study also may have fostered false hope about ADHD children’s prospects by pairing the NIMH findings with another study showing that children who started school with behavior problems performed at the same academic levels as their less troubled peers by the time they reached the upper-elementary grades.
“The coupling with disruptive behavior wasn’t very helpful,” Dr. Shaw said. “They’re not the same problems.”
The second study, published last month in the journal Developmental Psychology, focused on kindergartners who had been disruptive, withdrawn, aggressive, or found it hard to get along with peers.
Children who had problems with attention control were also addressed in that study, but their academic outcomes were slightly different.
Judith Warner, who writes a blog on parenting for the Web site of The New York Times, posted a critique of the paper’s own coverage of the research.
The Role of Medication
The Times story, which ran Nov. 13, prompted e-mails from readers who saw the NIMH findings as evidence against the common practice of prescribing medication for children with ADHD, even though the study did not address that issue.
Dr. Shaw said he did not see the study as having immediate implications for how children with ADHD should be treated, either medically or in the classroom
Sydney S. Zentall, a professor of special education and psychological sciences at Purdue University, in West Lafayette, Ind., agreed.
“The only reason most of us would use findings like this in our presentations [to special educators],” she said, “is to counter the long-prevalent belief that ADHD doesn’t exist, that it’s a social phenomenon, or spoiled children, or poor parenting.”
Dr. Shaw and his research team plan to keep studying the children in the study into their late teens, paying special heed to those who seem to grow out of the symptoms.
“Once we know what the brain mechanisms are of recovery, then we can see if those are the kinds of things we can boost through intervention,” he said.
Vol. 27, Issue 14, Pages 1, 14Published in Print: December 5, 2007, as ADHD Experts Fear Brain-Growth Study Being Misconstrued