Biological Evidence Underpinning ADHD

For decades, attention-deficit hyperactivityprogress in the quest to solidify the dynamics of
disorder has sparked debate. Is it a biologicalADHD. "It's a big deal to get this kind of
illness, the dangerous legacy of genes ornonmedicated sample," he added.
environmental toxins, or a mere alibi for brattyToo Much Diagnosis?
kids, incompetent parents and a fraying socialThe mainstream scientific consensus is that, as
fabric? With 4.5 million U.S. children having receivedwith other mental illnesses, there's no blood test
a diagnosis of the disorder -- and more than halfor brain scan that proves an individual has ADHD.
of them taking prescription drugs to control it --The disorder instead is diagnosed via a checklist
the question has divided doctors and patients,of troublesome behaviors, including impulsivity,
parents and teachers, and mothers and fathers.daydreaming and forgetfulness. What makes the
Scientists maintain that they've been narrowing indiagnosis particularly difficult, Hinshaw said, is that
on the origins and mechanics of disablingthose behaviors all fall within the normal range of
distraction, while gathering increasing evidence thathuman behavior. People with ADHD are simply
ADHD is as real as such less controversialfarther out on the spectrum, and, often, enough
disorders as Down syndrome and schizophrenia.so as to wind up in constant trouble. In addition,
Their most recent progress is described in a Sept.symptoms typical of ADHD can also stem from
9 report in the Journal of the American Medicalother illnesses or injuries. Swanson said scientists
Association, based on a new study that indicatesare probably years away from a biological test
a striking difference in the brain's motivationalfor the disorder, though the new study is a step
machinery in people with ADHD symptoms.in that direction.
"This is another big piece in the puzzle saying thatResearchers say they've been closing in on
there is something there, that this is not simply abiological differences in people with ADHD, including
matter of anxious parents," said James Swanson,genetic roots -- some scientists have found the
a co-author of the report and a developmentaldisorder to be more hereditary than schizophrenia
psychologist based at the University of Californiaand only somewhat less so than height -- and
at Irvine.even the relative size of certain brain structures in
'An Interest Deficit'childhood.
The JAMA study said that, compared with aPopular skepticism persists, with critics ranging
group of healthy subjects, brain scans of 53from the extreme of Scientologists, who militantly
adults with ADHD revealed a flaw in the wayoppose psychiatry in general, to more mainstream
they process dopamine, which among othervoices saying the disorder may exist but is
things, alerts people to new information and helpsover-diagnosed -- meaning that the powerful
them anticipate pleasure and rewards. Swansonmedications used to treat it are being, in essence,
speculated that people with ADHD may evenabused.
have a net deficit of dopamine."My position is that this is a parenting issue," said
The findings offer support for a long-held theoryJohn Rosemond, the psychologist who writes the
about why people with ADHD tend to be so easilynationally syndicated column "Traditional Parenting"
distracted and bored -- so hard to teach in school,and calls ADHD a "fiction." Rosemond said he
so prone to end up in high-stimulus jobs such as inhadn't yet read about the dopamine study, but, in
sales or the media, and so susceptible to gamblinga phrase frequently used by naysayers,
and drug abuse. According to the theory, themaintained that the symptoms associated with
trouble is a lack of motivation as well as a deficitADHD "describe a typical toddler."
of attention: People with the disorder can'tVolkow acknowledged that sometimes ADHD is
generate the same degree of enthusiasm asapplied to children who don't fit the medical
other people for activities they don't automaticallycriteria, including bright kids who misbehave when
find appealing.they get bored. But she added that the disorder
"Parents always wonder why their children withis at least just as often under-diagnosed, in which
ADHD can skateboard for hours and practice thecase, she said, "the tremendous misinformation"
same thing over and over but can't stay on taskpromulgated by critics does harm to people who
in school," said Swanson, who said he and fellowought to be getting help. Longitudinal studies have
researchers have taken to calling the syndromeshown that untreated children with ADHD are
"an interest deficit."substantially more prone than those without it to
The project was led by Nora Volkow, a researcha long list of dangerous outcomes, including drug
psychiatrist who is director of the Nationaland alcohol abuse, academic failure, car accidents
Institute on Drug Abuse, together with scientistsand teen pregnancies.
affiliated with institutions including the BrookhavenThe syndrome first appeared in the psychiatrists'
National Laboratory and the Mount Sinai Medicalatlas, the Diagnostic and Statistical Manual of
Center. It took eight years to complete, mostlyMental Disorders, in 1987, replacing "attention
owing to the difficulty of finding people withdeficit disorder," which is still frequently used by
diagnosed ADHD who had never taken medicationauthors and other commentators. In previous
or recreational drugs, which might have subtlydecades, the same group of symptoms had been
changed their brains, and had no history of otherreferred to with names including "minimal brain
serious psychiatric illness. Children weren't involveddysfunction" and "hyperkinetic impulse disorder."
because of regulations against subjecting minorsProgress in the search for biomedical markers for
to unnecessary radiation.ADHD might seem to help justify medication,
Volkow's team collected detailed images ofincluding pharmaceutical stimulants, now the most
participants' brains with positron emissioncommon U.S. intervention. Indeed, research has
tomography, or PET, scans after injecting themshown that stimulants help alleviate the classic
with a radioactive chemical that binds to dopamineADHD symptoms in the majority of cases.
receptors and transporters, which take up andVolkow, nonetheless, said she believes in trying
recycle dopamine as it moves between neurons.behavioral therapies first, using drugs only if those
The imaging showed that, in people with ADHD,aren't effective. She said her team's findings
the receptors and transporters are significantlyunderscored the value of having teachers be as
less abundant in mid-brain structures composingengaging as possible and of having parents
the so-called reward pathway, which is involved inreinforce good behavior with skillful praise and
associating stimuli with pleasurable expectations.rewards.
Stephen Hinshaw, chair of the psychology"Our brains are hard-wired to respond to bribes,"
department at the University of California atshe said.
Berkeley, praised the study as being "above andAnd that goes even more so, apparently, for
beyond the normal rank and file" of incrementalbrains with ADHD.