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what is adhd?

russell barkley

Professor of psychiatry and neurology at the University of Massachusetts Medical Center in Worcester. Author of numerous books on ADHD, including ADHD and the Nature of Self-Control and Attention-Deficit Hyperactivity Disorder: A Handbook for Diagnosis and Treatment.
read FRONTLINE's interview with barkley
You've been a psychologist since 1973. How has your profession evolved in relation to ADHD?

I've been involved in doing research since 1973. I've been a licensed psychologist since 1977, but I've devoted my entire scientific career to studying children with ADHD. Over that period of time, I've seen several things in the field. Most importantly, the way we think about the disorder and conceptualize it has changed markedly.

Back in the 1950s and 1960s, we really thought . . . that these were children who moved around a lot and climbed on furniture and couldn't control their activity level, and we called them hyperactive children. We then learned in the 1970s and the 1980s that they had tremendous problems with inhibitions, with impulse control. They can't stop and think before they act. They say things without regard to what's going to happen to them for saying or doing those things. We also found they had tremendous problems with being distractible and inattentive. So our view of the disorder expanded greatly over that period of time.

It's now evolved to a point where we have begun to see ADHD as a deeper problem with how children develop self-regulation and self-control. These problems with activity level, and later, with attention span and with impulse control, are simply the more superficial manifestations of a deeper developmental disorder, and with how the children go on to develop self-regulation--the ability to control your own behavior for social purposes.

We've also changed our understanding of the etiology of ADHD. . . . Back in the 1950s and 1960s, we didn't know what caused it. There was a suspicion that maybe bad parenting or social learning of some kind attributed to it. Other people thought it was just an immature personality development, and that within a few years, these children would outgrow the problem by the time they were adolescents.

We know now, thanks to a number of studies over the last decade, that ADHD is a real developmental disorder; that it's largely biological and genetics contribute to the disorder; and that it's the most inherited of all the psychiatric disorders, rivaled only by autism in terms of its genetic contribution to it. And we're beginning to focus now on three critical brain structures that seem to be implicated in this disorder. ...

Is this a mental illness?

Well, it depends on how you want to define a mental illness. I prefer to call it a developmental disability, because, like mental retardation, like the learning disabilities such as dyslexia and autism, it comes on very early. It appears to be a problem with the way the brain is developing. It affects the child's life in many different capacities, and it has long-term consequences for the individual. So, in that sense, it's very much like the other developmental disabilities that we know so much about.

It is classified as a mental illness by the American Psychiatric Association, and it is placed in their manual of mental disorders as such. But that's just a matter of classification. I think more scientists view it really as being akin to the developmental disabilities, rather than being more like schizophrenia or bipolar disorder, where there's some, perhaps, gross abnormality in the individual's development. Here, instead, what we're seeing is an immaturity and a failure to develop as quickly as other people in these critical areas of personality development and self-control.

A lot of people--such as parents--feel very uncomfortable with the label. Is it important to label it?

Well, labeling is a two-edged sword. Of course, it brings with it all the negative connotations. You're being singled out; you'll be stigmatized. It is a label that is mentioned in psychiatric textbooks as a mental disorder, and, of course, people are afraid of stigmatizing their children so young in life with the label of a mental disorder. But on the other hand, there is the upside to labeling, an upside that we can't avoid, and that's why we continue to use labels.

First of all, by using a precise label, we can connect this group of individuals up with a large body of scientific knowledge about other people with this label and with this disorder. So if we use this label, it brings with it a tremendous amount of information that can help the individual better understand their disorder and how best to manage it. If we start labeling it with some euphemism, some ambiguous personality term like, they're just "high-energy children," you've disconnected immediately from this larger body of accurate scientific knowledge that we have. And that's a disservice to these people.

The other disservice it will do is that there are rights, protections and access to services that people with ADHD have a right to now because of various legislation that has been passed to protect them. There are special education laws. And the Americans with Disabilities Act, for example, mentions ADHD as being an eligible condition. If you change the label, and again refer to it as just some variation in normal temperament, these people will lose access to these services, and will lose these hard-won protections that keep them from being discriminated against. . . .

peter jensen

Formerly the head of child psychiatry at the National Institute of Mental Health, Jensen was the principal author of the landmark NIMH study NIMH, the Multimodal Treatment Study of Children with Attention Deficit Hyperactivity Disorder (MTA). He is now the director of Columbia University's Center for the Advancement of Children's Mental Health.
read FRONTLINE's interview with jensen
Some people would argue that the medications were actually discovered before the diagnosis was sort of fine-tuned, so therefore the diagnosis was made to fit the medication. What would you say to that?

Some people have suggested that the ADHD diagnosis was invented to fit a drug. This is bizarre. In actual fact, the syndrome was described back as early as the 1900s, and we have other reports going way back. It's true the label has changed, but the classic core symptoms haven't really changed hardly a smidgen. And so when people go back and they study "the hyperkinetic reaction of childhood" and "minimal brain dysfunction and damage--these are the same children; it's quite clear. . . .

What was the conclusion of the panel convened by the National Institute of Health in 1998 to determine a consensus on diagnosing and treating ADHD?

... I've been asked several times to kind of consolidate or collapse what I felt the statement said. Basically, it said that there's some validity for the diagnosis of ADHD as a disorder, and that just to kind of kick it full of holes would be a little bit inappropriate. We don't know exactly whether to call it a very severe behavior problem, a mild behavior problem, or a severe medical disorder. Where do you draw that cut?

. . . The Consensus Conference said, "It appears to be a valid disorder. It can be reliably diagnosed. But we need more work on that." That's what they said. But then they went on to say, "It has bad outcomes, it's severely impairing and it's a major public health problem." And so I was real pleased, because I thought, "You know, as a society, we can't ignore it. We can't just say it's not a public health problem, because it is a public health problem, and it has those severe outcomes for many of these children."

Then it went on to say that the treatments are safe and effective, in the short term. It said the medicines work and the behavior therapy works, and it said that the medicines tend to be more effective than the behavior therapies in short-term trials. But some people were disappointed that it didn't say, ". . . and so everybody should use medicine." They said, "No, we don't want to say that." It was an objective group of scientists. . . . If Peter Breggin had his way, he would have said, "Never use medicine." . . .

It pointed out some important gaps. It said, "We don't know enough about long-term safety, and the federal government should do more." Well, that's a win for parents as far as I'm concerned, because that means that parents have an agenda. . . . They should be asking the federal government to do better long-term studies. . . .

Two other things it said--and I was very pleased about them, because it showed the warts--it said, "The way we're treating these children is a mess. . . . Everybody's not working together, and our system isn't working together very effectively. We need better systems for these children." That wasn't a feel-good message. . . . The other non-feel-good message was for the scientists. The report said, "You guys don't know anything about how to prevent this disorder, and you're not studying it. Start working on prevention." . . .

russell barkley

There are studies, like the NIH Consensus Statement on diagnosing and treating ADHD, that question the diagnosis. A panel of experts concluded that we know something, but not everything.

Let me point out two things. The consensus conference that was held earlier and sponsored by a number of organizations, including NIH, was a reasonable idea. But it was seriously flawed from the start, and you have to keep these flaws in mind in understanding this document.

First of all, it was a political activity, not a scientific activity. The experts that were chosen to review the literature are not experts in ADHD. They are practicing professionals in other fields of science, or are simply clinical practitioners. They are certain not experts in ADHD. Experts, people like myself and others, were called to present our information to the panel. But the panel itself was not a body of experts, and it shouldn't be misrepresented as such. That also leads to problems, because you have people who don't know the literature trying to understand what the science has to say within just a few days.

. . . Because it was a political document, it also had to include phrasing that was a bit of a bone to the critics of ADHD, tossing them a certain kind of sentence here and there so that they wouldn't feel misrepresented in the panel discussions. But many scientists would not have put those phrases in there, because they make it sound like we know less than we really do about this disorder.

peter jensen

Someone described to me the NIH Consensus being a group of 12 scientists that had 6 days to evaluate 6,000 studies. And while they were good scientists, they had never thought about the same things you have to think about every day as a clinician, because they have other fields of interest. Can you respond to that?

If you want to get objective scientists, they can't really be publishing in the area of ADHD. They might be publishing in the area of pediatric developmental disabilities. It's nice to know about children; it's nice to know about what constitutes a good clinical trial. . . . That expertise is needed.

Now, I, and many other scientists like myself, are often called upon to review areas we don't know well. And while we can't review the area as well in terms of the specific disorder, we can refute the quality of the study. We can say, "Is the data emerging from this study based on solid scientific design of a study, on good principles of measurement?"

. . . They didn't have just six days. Actually, they had six weeks, because we gave them the literature well ahead of time, and their job was to review that literature ahead of time and to be informed and read more and more. Now, in those two days, they had to review the testimony that was actually delivered face to face. . . . Scientists are busy, and I can't say how well every scientist reviewed the data. But they were scientists and their reputations were on the line, and so I trust ethical scientists, who are known for their good thinking, to do that. But it's an imperfect process. Could they have missed some things? Oh, absolutely. Could they have underestimated the value of some of the evidence? Absolutely. . . .

lawerence diller

Author of Running on Ritalin, Diller received his medical degree from Columbia University's College of Physicians and Surgeons. While he has diagnosed some children in his private practice with ADHD, Diller has criticized the proliferation of the ADHD diagnosis and the rise of "cosmetic psychopharmacology."
read FRONTLINE's interview with diller
In your view, what is ADHD?

First of all, it's basically a subjective experience of a child who has extra trouble with inattention, impulsivity, and hyperactivity.

"A subjective experience of a child." What do you mean by that?

Well, it depends on who's doing the deciding, and in what environment and culture these people are living in.

Why don't we just test them? You just test them. That's what parents are told--you test them. What's subjective about it?

There is no test, unlike a blood test or brain scan that defines a gold standard for ADHD. That said . . . we see a very hyperactive kid running around the room, and usually they have other problems. They might have learning disorders, or might be mildly mentally retarded, or whatever. And you and I would have no problem agreeing there's something wrong with that kid. It's probably partly his brain.

But I tell you, the kids who I see who sit there like this, and they answer my questions beautifully, and they do really quite decently outside of school, or non-academic endeavors at home. And yet they're still struggling in school. Depending on the family, depending on the community, I might wind up giving that kid Ritalin. Does he have ADHD? Well, it's an eye-of-the-beholder decision. . . . There is no brain scan. There is no blood test that definitively says who has ADD and who doesn't. . . . The decision where to draw the line between abnormal and normal variance of behavior is an arbitrary one. ...

. . . It's enormously frustrating for a parent to face these kinds of answers, because there's no clarity. I don't know what to do. I'm a parent; I have children. I wouldn't know what to do after listening to what you said.

People want clarity. And that's the seduction of the biological model. And I think that's one of the reasons why in our particular technological society, this has great attraction. But parents also worry. I think there are a couple of things that parents can do to try to stay sensible about this. I think if they're getting a prescription after 15 or 20 minutes of talking to the doctor, then they know that is going to be a very, very limited evaluation. And all the interventions that follow are going to be very, very, limited. A good, decent ADHD evaluation takes a couple of hours. And almost everyone agrees with that. . . .

I think another thing that evaluators and families are often overlooking is the absence of participation of fathers--if they're associated with the children in the family, or still have a connection with the child. . . . And I think too many evaluations go on with only the mothers involved. . . . The likelihood of that medication being used properly goes way up when we have both parents involved in the process.

The other major problem in terms of an evaluation is what's been termed a structural divide--between schools and teachers, who make the complaints about the child, the doctors who prescribe the medications, and the parents, who are the couriers in between. Unfortunately, a lot is lost in both directions. Concerns that the teacher has, or views that the teacher has, get mediated through the parent's worries, or lack of worries. Ideas that the doctor has, both on medication and other interventions, don't get translated either. So there's this structural divide. . . .


A child psychologist, Parker founded Children and Adults with ADD (CHADD), a nonprofit organization. He lobbies frequently on behalf of CHADD in Washington, D.C., and is now the president of ADD Warehouse, a company that sells ADHD materials.
read FRONTLINE's interview with parker
Is ADHD solely a biological disorder? Does it have elements of bad parenting? What's going on?

I think there's a combination of causes for ADHD. It's really a neuropsychological or biosocial kind of phenomenon. Many children with ADHD come by it through genetics. In a large number of children, it's inherited, but certainly the environment plays an important role as well. Parenting certainly can improve the condition or cause more difficulties. But largely this is not the result of poor parenting; it's more the result of a combination of environmental and social, as well as genetic influences upon the child.

Could this possibly be a disorder that has risen because of the amount of social stresses that families are undergoing nowadays?

I think that the amount of stress in our social environment right now, with our fast-paced lifestyles and busy working parents, causes additional problems in child-rearing for a lot of families. It increases the likelihood that children are going to be under more stress and anxiety. But that by itself doesn't cause ADHD. That may aggravate a situation for a child who does have attentional problems and behavioral problems, because these children require a tremendous amount of care, attention and supervision, and oftentimes, parents don't have that time to give to them. ...

A lot of people insist that all of this is just a fraud, that this has been devised by a pharmaceutical industry and a psychiatric community that wants to make more money, and that simply wants to drive an industry. What do you say to that?

Those people who think ADHD is a fraudulent disorder, a disorder that was concocted to be self-serving to pharmaceutical industries or others, don't understand the suffering that parents feel with child who's affected by ADHD. They don't understand the outcomes that these children suffer themselves as they grow up. ... This is a very serious problem, and it's about time we took it seriously. ...

Thank goodness there are effective treatments out there that can help these families and help these adults. Instead of claiming that the rise in the medication use is so astounding, we should be saying, "My goodness, thank God they're finding more of these children and recognizing them earlier on, and providing appropriate treatment for them." That's where the emphasis should be, not wasting our time and wasting our resources and wasting families' lives on fraudulent skeptical claims. ...

There's been a good deal of science in the last few years in terms of studying brain function, brain structure and brain chemistry that has pointed the way towards differences in children with ADHD versus non-ADHD children ... There's been solid research pointing in the direction of a neuro-biological cause for ADHD. There's also strong evidence that ADHD is highly heritable. If you look at twin studies, studies of large samples of identical twins, we see that the likelihood that if one twin has ADHD there's a strong likelihood--90 percent or more--that the other twin is going to have ADHD, even if raised in a different environment. Thirdly, if you look at studies of adopted children, we see that adopted children [who are ADHD] resemble more their biological parents than they do their adoptive parents in terms of hyperactivity or impulsivity and inattention. Fourthly, there's been a large number of studies on medications that affect brain chemistry and their success in treating ADHD. All these findings point very, very, very strongly to a neurological or neuro-biological basis for this condition.

russell barkley

Are there studies that indicate an element of the brain that might be different?

We think that the brain is very much involved in ADHD, for a number of good reasons. First of all, for many years, an extensive amount of research shows that the kinds of electrical activity that we can monitor . . . indicates that certain portions of the brain, particularly the right frontal area, are less active, less mature. They're under-aroused more than they should be, and we've known this for a long time. Other studies, also using brain electrical activity, indicate that the brain doesn't respond as quickly to certain kinds of stimulation, particularly stimulus to stop and inhibit their behavior. And so we have a large amount of research there as well.

More recent studies using blood flow have indicated that these critical regions in the brain that I'm referring to are less active than they should be, and aren't calling for as much blood as they ought to in order to keep themselves activated. More recently we've used magnetic resonance imaging (MRI) technology, to image the brain. And several studies now indicate that these structures are less developed, less mature. They're smaller in people with ADHD than they ought to be.

Finally, using the most recent technology called "functional MRI," studies are now indicating that these brain regions are substantially less active than they ought to be for someone of that age group. So we have multiple lines of information that converge on a common conclusion: that we have three regions in the brain that are less developed, less active than they should be; and, it turns out, that these regions are absolutely crucial for inhibitions and for thinking before you act--for self-control.

So this is a biological disorder.

It's largely a biological disorder. It has many causes, but all of the known causes fall within the realm of neurology and genetics. We can rule out the social environment, such as bad parenting, intolerant teachers, the breakdown of the American family, a decline in family values, excess amount of TV viewing or video games. These have all been proposed as causes of ADHD. But there's no evidence that we can find that will substantiate them.

All of the evidence that keeps turning up in our research points to genetics and neurology as being largely responsible for the excessive behavior and the poor self-control that we see in these children. So I think we can safely say that what we've learned in the past ten years is that environmental causes of ADHD are not credible. They do not account for the substantial amount of scientific findings that exist on this disorder today.


Castellanos is a pediatrician and child psychiatrist conducting neuroimaging and genetic studies of ADHD. He is the head of ADHD research at the National Institute of Mental Health (NIMH).
read FRONTLINE's interview with castellanos
There are a lot of theories about what ADHD is. Could you define for me what ADHD is?

ADHD is defined as symptoms of hyperactivity, impulsivity, and inattention beyond what's usual for a developmental age. A six-year-old is expected to be more hyperactive than a ten-year-old. But a six-year-old with ADHD can be much more hyperactive than a six-year-old without ADHD in certain settings; likewise inattention; likewise impulsivity. Those are observed in the home, in school, in play situations. But we don't have a test. We don't have an objective way of definitively saying, "This person has ADHD, or does not," in part, because we don't really understand what it is. . . .

How does ADHD work on the brain? What do we know about it?

We don't yet know what's going on in ADHD. We've approached it in a number of different ways, and one way has been to look at what brain regions are smaller, or different. What we've found is that there are a few regions that are smaller in kids who have ADHD. There are other groups that are looking at functional MRI, or at SPECTA (Single Photon Emission Computomography), usually in adults who have ADHD. And most of the evidence converges and suggests that regions that are rich in dopamine are involved. And that's interesting, because dopamine is one of the chemicals that Ritalin boosts.

. . . What does dopamine have to do with any of this?

. . . Dopamine is an important signal that certain parts of the brain use to regulate movement. If you don't have dopamine in those brain regions, you develop Parkinson's disease. But it's also apparently used to send a signal that something important is happening. . . .

It used to be said that dopamine was the reward chemical--that if something was rewarding, then you would release dopamine. It turns out to be more complicated than that. It's not just whether something's going to feel good, or be rewarded; it's more if there's a possibility that something would feel good.

If an animal knows that they're going to be rewarded when they correctly do a task, then dopamine is no longer involved. But when the animal thinks that maybe this is the way to solve the task, dopamine is leading the way, saying, "This, try this, try this." So it's a very important signaling molecule. And it's classified officially, I guess, or technically, as a neurotransmitter. But it's probably more appropriately described as a neuro-modulator, which means that it sets or modulates the tone for these complex systems.

So we think that it's important to have optimal levels of dopamine in various brain regions; if they're not optimal, then things don't work as well. So that's a very sort of cut-and-dried, simplistic possible explanation of what's going on in dopamine and ADHD.

. . . If I have ADHD, what do I have in my brain? A deficiency of dopamine? A small cerebellum?

The leading theory is probably that, effectively, your brain doesn't save its dopamine and use it as well as it might. Now, that's not been conclusively shown. There are two studies in adults with ADHD that suggest that that's true in the basal ganglia. And because they use radiation, it's going to be very difficult to repeat those studies in children. But it is sort of exciting to have that new information.

In fact, in one of the studies, they took individuals who had never been treated for their ADHD, tested them, and then gave them Ritalin and re-tested them--and found that the Ritalin, in fact, did affect the molecule that they were trying to have an effect on. And the result of that should be an increase in dopamine in the basal ganglia--we know in the basal ganglia, because we can measure it. We don't know what's going on in the frontal lobes; we don't know what's going on in the cerebellum, because there's much less dopamine there, and so it's much more difficult to measure.

So it's only a partial answer. If you're an adult with ADHD, I can make some tentative conclusions. But if you're a child with ADHD, I don't yet know what's going on in your brain. ...

Give me one true fact about ADHD.

The posterior inferior vermis of the cerebellum is smaller in ADHD. I think that that is a true fact. It's taken about five years to convince myself that that's the case. That's about as much as I know--that I'm confident about.

What does that mean?

I don't know what it means, but it's true, and it's a fact. And that's the next step. ...

Even though [the cerebellum is] only about 10 percent of the size of the total brain, there are more neurons in the cerebellum than in the entire rest of the brain combined, which is fascinating. But the cerebellum has never been thought to be that important, because you can remove it, and nothing terrible happens. But recently, people have noticed that the cerebellum is very involved.

One person says that the cerebellum is a little bit like a co-processor--it's useful, but it's not necessary. And he believes that its function is really to help the other parts of the brain work better. That makes some sense to me, that maybe that's what's not working so well in ADHD. People with ADHD can do anything; they just don't do it quite so well. It's a disorder of efficiency, or inefficiency, as much as anything, I believe.

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