US New and World Report
May 6, 2002
The Mind Maze
Can
'distraction' be found in the brain's biochemistry?
In
the darkened office of Lexicor Health Systems in Boulder, Colo., 11-year-old
Shannon closes her dark brown eyes and sits quietly in her chair. She is wearing
a multicolored electrode-studded cap, which transmits the electrical impulses of
her brain to an electroencephalogram, or EEG. Behind her on a computer screen
scrawl 19 wild lines that represent the activity in several regions of her
brain. One would never surmise from Shannon's Zen-like demeanor what the brain
scan is detecting inside her head: that she is one of the more than 2 million
children in America who suffer from attention deficit hyperactivity disorder.
The
result of Shannon's session will be a QEEG–a "quantified EEG" that
will allow diagnosticians to statistically compare her brain with thousands of
others. What they are interested in, specifically, is the proportion of
low-frequency theta brain waves to much faster beta waves in a region of the
brain called the prefrontal cortex. Studies have suggested abnormalities in both
these rhythms associated with attention–or lack of it. Children produce a lot
of low-frequency theta brain rhythms when they struggle to concentrate, and when
their concentration is overwhelmed by too much stimulation they produce the
speedier beta waves. By comparing what Shannon's brain does with both
"normal" brains and those of others who have been diagnosed with ADHD,
researchers at Lexicor are hoping for the first time to provide a quantitative
tool to help identify this vexing disorder.
Genetic
mystery.
The QEEG may never become the "gold standard" in diagnosing ADHD. But
it illustrates how increasingly sophisticated understanding of brain activity
may offer clinicians greater confidence in their diagnosis. It may also hold out
promise for the 20 percent of children diagnosed with ADHD who do not respond to
the usual stimulant treatment–by identifying a pool of symptoms that they all
might share. Clearly, genes play a role in ADHD, because it runs strongly in
families, but no ADHD gene has yet been identified. Lacking that kind of
definitive diagnostic tool, a deeper understanding of the neurology underlying
the disorder could help clinicians untangle true ADHD from accompanying
disorders and disorders that resemble it. Indeed, QEEG is one of several
brain-scanning technologies now being deployed to home in on the unique
properties of the distracted mind.
Such
objectivity would be a godsend for parents. "There is not a single test
that we have, no rating scale, no brain scan, there is nothing that will tell
you yes or no about ADHD," says Thomas Brown, associate director of the
Yale Clinic for Attention and Related Disorders. That's because, like most
mental disorders–depression, anxiety–attention disorder is a "spectrum
diagnosis": Its widely varying symptoms are a challenge even to the most
skilled clinician. Is this atten- tion problem really disabling or merely within
the parameters of "normal"? How do disorders like learning
disabilities–which tend to accompany many ADHD diagnoses–compromise
attention? And could the problem not be ADHD at all but what doctors call
"mimics"? Mimics can be biological (sleep deprivation), psychological
(anxiety or depression), or social (a child's response to poor parenting or
teaching). Or is ADHD, as some critics contend, a culturally bound diagnosis of
"boyhood"? "Lots of people confuse having the symptoms with
having the disorder," says Mark Stein, the chief of psychology at the
Children's National Medical Center in Washington, D.C.
Ritual
Rx.
As a girl, Shannon is outnumbered more than 2 to 1 by boys in having attention
disorder. But her clinical journey has not been that different. In an office
next door to Shannon's examination room, her mother pulls out a thick file. Over
an inch of paperwork charts her daughter's trajectory from classrooms to
doctors' offices to psychologists' offices. And she is actually one of the lucky
ones. Some parents simply get first complaints and then testing reports from a
teacher, and then turn to their pediatrician to fix the problem. The
pediatrician typically decides to prescribe the stimulant medication Ritalin to
see if the child responds–a practice as common as it is dangerous. "You
don't want to make a diagnosis based solely on treatment response," says
Lenard Adler, the director of the ADHD program at New York University.
Sometimes
it's difficult to be confident in a diagnosis for a murky disorder. ADHD
typically involves a triad of symptoms that are themselves subject to
interpretation: the inability to sustain attention, difficulty in controlling
impulsivity, and, sometimes, hyperactivity. According to the DSM-IV, the
diagnostic bible of the American Psychiatric Association, symptoms can range
from frequently losing things to persistent difficulty in completing tasks.
Moreover, many children who have ADHD are not hyperactive at all. "In the
past, parents and children were given a moral diagnosis," says Edward
Hallowell, a Harvard psychiatrist and author of Driven to Distraction. "The child was seen as bad, stupid,
wayward, weak, or the product of bad parenting. Now we know that powerful brains
typically have powerful vulnerabilities and powerful strengths.''
Given
the complexity of the brain's attention and thinking mechanisms, the prevalence
of the disorder is not surprising. "There is so much complicated
communication in the brain, with different parts talking to each other,"
says Timothy Wilens, a staff psychiatrist at Massachusetts General Hospital,
"that it is not easy to get unification." For example, many studies
suggest that the reduced frontal-lobe activity in ADHD may be caused in turn by
decreased activity in the basal ganglia, a deeper part of the forebrain that
generates two important neurotransmitters called dopamine and norepinephrine.
Studies suggest that abnormally low supplies of these chemicals may be involved
in inattention. Indeed, the theory behind stimulant medications is that they
adhere to and activate these illusive neurotransmitters and, through a cascade
of neuronal events, "light up" the prefrontal cortex.
Back
in Boulder, her electrical beanie off, Shannon is playing on a computer. Her
mother collects her files, anticipating that she will be able to confirm exactly
what is going on in her daughter's brain. And in the process put her own mind at
rest: "I ended up feeling as if the problem had to do with me as a
parent,'' she says. "Now that we can quantify and seal the diagnosis, I
feel more confident in what we can do about it."