Some people who commented on that post objected to my sociological analysis by referring to evidence that the brains of people diagnosed with ADHD are in some ways different from those of other people. To them, the evidence of a brain difference is somehow proof that ADHD is a "medical" or "biological" disorder and that a sociological analysis of it is out of place. But if you give it some thought, you will quickly realize that there is no contradiction at all between biological and sociological analyses of ADHD or any other condition referred to as a disorder. My goal in that essay was to explain the extraordinary increase in rate of ADHD diagnosis that has occurred over the last two or three decades. I don't think that increase is primarily due to a change in brain structures in the general population; I think it is primarily due to a change in social values and especially in the conditions of schooling. Today, as a society, we are far less tolerant of children who don't adapt well to our system of compulsory education than we were in the past, and so we diagnose them and give them drugs.
For a somewhat (but not fully) analogous case, consider homosexuality. Homosexuality is biologically a condition of the brain; but the decision to label it as a disorder, or not a disorder, is a social judgment. Until 1973, homosexuality was on the American Psychiatric Association's list of official mental disorders, but in that year it was removed. Suddenly, gay people were no longer "disordered." That decision clearly reflected a change in social values, a change that made it possible for people with the brain condition of homosexuality to live happier lives than they had been able to before, when they more or less had to stay in the closet and were subject to terrible abuse and even arrest if they did not. With regard to homosexuality we have as a society become more liberal and accepting. With regard to the kind of childhood rambunctiousness and impulsiveness that leads to a diagnosis of ADHD, however, we have as a society become less liberal and accepting.
The story for ADHD, of course, is not fully analogous to that for homosexuality. The condition we call ADHD is clearly one that can vary in degree. A few people--and I think that is very few people--who are diagnosed with ADHD have the condition to such an extreme degree that most of us would consider it to be a disorder, worthy of some kind of treatment, under almost any social conditions. But most people with the diagnosis have the condition to a much lesser degree than that--a degree that interferes especially with schooling and certain other school-like activities, as they are structured today, but may actually be helpful in other settings.
In the remainder of this essay I'll describe briefly current thinking concerning the cognitive and neural foundations for ADHD and explain further why I think our focus should be on changing our system of schooling to accommodate children's diversity rather than on changing children's brain physiology to accommodate schooling.
The basic cognitive characteristic of ADHD appears to be high impulsiveness and reduced "executive control."
According to the most widely accepted cognitive model of it, the fundamental problem in ADHD is not one of attention so much as one of impulsiveness. By a wide variety of measures, people diagnosed with ADHD are more impulsive, less reflective and controlled, than other people. This impulsiveness is believed to underlie all or most of the distinguishing behavioral characteristics shown by such people. Impulsiveness leads them to be easily distractible, which is why they are seen as inattentive. It also leads them to be impatient and restless, unable to tolerate tedium or to sit still unless something truly grabs and retains their interest, which is why they may be seen as hyperactive. And it leads them to be highly emotionally reactive; they tend to respond immediately, emotionally, overtly, to stressful or otherwise arousing situations. The model is no doubt overly simplistic, but it is nevertheless useful as a beginning point for thinking and talking about ADHD.
Cognitive psychologists and neuroscientists commonly use the term executive control to label the mechanisms by which the brain inhibits impulsive behavior, reflects, and then acts on the basis of reflection rather than impulse. Although executive control is generally thought of as a good thing, it seems obvious that it can also, if too strong, be a bad thing. The opposite of impulsive is inhibited. Some people are too inhibited for their own good. They stew constantly over what is the right thing to do, or over the possible negative consequences of every alternative, and therefore they don't do anything. While the highly controlled person sits and watches an emergency, trying to figure out the best possible response and worrying about the risks, the impulsive person jumps in and saves someone's life.
The value of diversity along the controlled-impulsive personality dimension
Most psychologists would say that psychological wellbeing is maximized by a certain optimal degree of executive control. The overly controlled person suffers from too much inhibition, and the overly impulsive person suffers from too little of it. I agree with that when we are talking about extremes. However, between the extremes there is a broad range on the control-impulsiveness dimension that is potentially quite compatible with psychological wellbeing and contribution to society. The trick, for each person, is to find niches within their environment that play to their strengths rather than to their weaknesses. In general, people who are highly controlled are great in jobs that require lots of reflection and relatively little action, and people who are highly impulsive are great in jobs that require lots of action with relatively little time for reflection. This has nothing to do with degree of intelligence. You can be intelligent and impulsive, making terrific snap judgments; and you can also be intelligent and reflective, making good judgments after thinking things through very carefully.
We are a highly social species. Never in our evolution as humans did we survive on our own, as separate individuals. We always depended on our cooperative relationships with others, and the same is true today. From this point of view, it is not surprising that natural selection would have supported a broad range of personality types. People of different personalities are well adapted to make different kinds of contributions to the community (and, thereby, also to themselves). Ideally, they would all be valued for the unique contributions they can make and would be helped by others in their areas of weakness. Certainly this was true in hunter-gatherer bands, and we see it operating today within healthy families, tight-knit friendship groups, and well-run businesses. The dimension of control versus impulsivity is, I suggest, one of the most obvious and important dimensions of normal, healthy personality variation. In the course of our evolution, it was valuable that some of us were relatively more controlled and reflective while others of us were relatively less controlled and more action-oriented than the majority.
It is not hard at all to think of conditions in which ADHD-like characteristics are socially valuable. Distractibility may result in efficient monitoring of changes in the environment, so that sudden dangers or new opportunities, which others would have missed, are detected. Impatience may be a valuable counterweight to the tendency to dwell too long on a way of thinking or behaving that isn't going anywhere. Impulsive action may underlie bravery in the face of dangers that would keep others immobile. Difficulty following instructions may imply independence of mind, which can lead to novel ways of seeing and doing things. Emotional reactivity may be a good counterweight to the tendency of overly controlled people to hold in their emotions and ruminate. One thing I have observed (informally) in people diagnosed with ADHD is that they rarely hold grudges; they let their emotions out and then get over it.
But in school, of course, all of these things are bad; they all get you into trouble. School--at least school as usually defined these days--is a place where you must concentrate on what you are told to concentrate on, no matter how tedious; follow the teachers' directions, no matter how inane; complete assignments for the sheer purpose of completing them, even though they accomplish nothing useful; and, while doing all of that, control your emotions. The school classroom is not a place that values bravery, inventiveness, independence of mind, or emotional reactivity. So, of course, impulsiveness comes across as a "disorder" in school. Today we tend to define school as the primary environment of the child, so impulsiveness is the number one mental disorder of childhood.
The brain system underlying the controlled-impulsive dimension appears to include the prefrontal cortex and to involve dopamine as a neurotransmitter.
Neuroscientists have made much-touted progress in understanding the brain, but still that understanding is extremely superficial. We have no idea, really, how the brain does any of the amazing things it does (beyond the simplest reflexes), but we do have some ideas about which parts of the brain are most involved in which functions. The areas of the brain that seem to be most crucial for executive control appear to lie within the prefrontal lobes of the cerebral cortex and in connections between the prefrontal cortex and other parts of the brain (including the striatum and the basal ganglia), which are involved in initiating and inhibiting actions. At least some of these neural connections involve dopamine as the predominant neurotransmitter, which is significant because the stimulant drugs used most often to treat ADHD--preparations of amphetamine or methylphenidate--all exert their effects by prolonging the action of dopamine in neural synapses.
Not surprisingly, therefore, researchers looking for brain correlates of ADHD have focused on the prefrontal cortex and on dopamine. The results of such research are highly variable from lab to lab, with much controversy resulting. Also, the results are often confounded because most of the people in the ADHD groups have been treated with stimulant drugs, either at the time of study or in the past, so it is not clear if any brain difference observed is a correlate of the ADHD itself or is caused by long-term effects of the drug. However, overall, the research suggests that people with ADHD, compared to other people, may have (a) slightly reduced neural mass in the prefrontal cortex, (b) reduced activity in some parts of the prefrontal cortex while performing certain tests of executive function; and (c) fewer dopamine receptors in certain parts of the brain that receive input from the prefrontal cortex. All of these differences are highly variable from individual to individual and observable only as a result of statistical averaging. So far no biological marker of ADHD has been found that is sufficiently reliable to be used as an aid in diagnosis.
The studies of brain differences are interesting, but they have no bearing at all on the question of whether ADHD is a disorder or a normal personality variation. All personality variations have a basis in the brain. Of course they do. The brain controls all of behavior, so any difference that is reflected in behavior must exist in the brain. The only means by which natural selection can produce personality variation is through altering genes that affect the brain. If people diagnosed with ADHD differ behaviorally in any consistent way from other people, then their brains must in some way be different. Even if the research to date showed no difference at all in the brains of people with and without an ADHD diagnosis, I would argue that a difference exists. The researchers just haven't looked in the right places, or with the right tools or systems of measurement.
The potential risks of the stimulant drugs used in ADHD treatment.
The stimulants used to treat ADHD are powerful drugs that alter radically the chemical environment of the brain, and we don't know their long-term effects in humans. Their immediate side effects are well documented. In degrees that vary from drug to drug and person to person, the drugs can cause insomnia, anorexia, weight loss, suppression of growth in young children, headaches, Tourette's Syndrome, dullness of mind, depression, psychotic episodes, and a host of other negative effects that the drug companies are required to list. Some people cannot tolerate the drugs at all because of these effects, but most, through experimentation, can find a stimulant drug and a dose that is tolerable.
The drugs do, in most people, improve school performance. Students complete more assignments and get higher grades when taking the drugs than when they don't. This is true even for students who are not unusually impulsive and have never been diagnosed with ADHD. That is why many non-ADHD students in high school and college take the drugs illicitly (they commonly get them from ADHD-diagnosed students who secretly aren't taking the drugs). There is no evidence that the drugs improve long-term learning and retention of information, but they definitely improve school performance and grades in the short run.
The use of stimulants to improve school performance is somewhat analogous to the use of steroids to improve athletic performance. In both cases the highly competitive environment promotes use of the drugs. Teachers, parents, and students themselves see that the drugs improve performance on standardized tests, and all regard that as a good thing. In our school-obsessed society, performance on such tests has become, more or less, the measure of a person's worth, so anything that improves such performance is worth the discomfort it may produce. Now, as preschools are becoming more and more like elementary schools, with assignments and tests, we are seeing a rapid rise in the number of preschool children--in the age range of 2 to 4--being given the drugs. Nobody knows what long-term effects the drugs may be having on those little children's developing brains.
In fact, nobody knows the long-term effects of the drugs on anyone's brain. One possibility, which has some research support, is that the drugs prevent the normal developmental processes that lead most people to become less impulsive, more controlled, as they grow beyond childhood and adolescence (I plan to discuss that more fully in my next post). Today we see more and more people who retain the diagnosis of ADHD into adulthood and continue to take stimulant drugs. Is that partly because many of those adults were taking stimulants during earlier stages of their development, which may have interfered with normal brain development? Studies with animals have shown quite clearly that the drugs can have such effects (I'll describe some of those studies in my next post), but so far studies testing this hypothesis in people have not been conducted.
In general, psychoactive drugs do have long-term effects, and most often those effects are in the direction of increasing long-term dependence on the drugs. An interesting and still controversial example concerns the use of antipsychotic drugs to treat schizophrenia. These have long been considered to be the wonder drugs of modern psychiatry, as they make patients with schizophrenia more manageable and often allow them to live independently outside of mental hospitals. On the other hand, we now know that in developing countries, where drug treatment for schizophrenia is much less common than it is in developed countries, people are much more likely to overcome the disorder as they grow older. One quite reasonable interpretation of this observation is that the drug treatments turn what would be a temporary condition into a chronic condition.
Might the same be true for ADHD? At this point we don't know. Drug companies have no incentive to conduct or support such studies--neither for schizophrenia nor for ADHD--and the studies required to answer the question would take too long and are too complex to make good doctoral dissertations. Even with the best of will, such studies are almost impossible to conduct in a way that produces clearly interpretable results. For ethical and legal reasons, you can't randomly assign people to different treatment conditions and follow them over a prolonged period, as would be required for a true experiment.
You can, however, conduct such experiments with animals, and the animal research to date suggests that the stimulant drugs indeed may produce long-term effects in the direction of prolonging the ADHD condition. In one study, George Ricaurte and his colleagues assigned one group of monkeys to treatment with Adderall (one of the most common drugs for ADHD) and assigned the other group to placebo treatment. They gave the Adderall orally, at a dose that produced the same blood level of drug that would normally be found in human beings treated for ADHD. After four weeks on Adderall they stopped the treatment for two weeks, then killed the animals and examined their brains. The main result was that the ADHD-treated monkeys showed a 30% to 50% reduction in dopamine and in dopamine transporter molecules in the striatum, which is one of the brain areas considered to be crucial for impulse control. At this point nobody knows what would happen with drug treatments longer than four weeks, and nobody knows if a longer period of recovery following termination of the drug would or would not result in a renewal of normal levels of striatal dopamine.
Given the unknowns and the suggested dangers that come from the animal research, I think we should err on the side of caution in treating ADHD with stimulant drugs. Our first line of attack should be to find alternative means of schooling, so that people can learn in their own chosen ways and are not judged by performance on standardized tests. Then, drug treatment should be reserved only for those few individuals who are so impulsive that they cannot function well or live happily in any of the niches available in our society.
In my last post I put out a call for stories about the experiences of people who have been diagnosed with ADHD and then have been homeschooled, unschooled, or transferred to a school (such as a Sudbury school) where students are in charge of their own learning. So far I've received about 20 such stories, mostly from homeschooling families. Before analyzing and writing about them, I'd like to receive more such stories, especially from those involved in unschooling or schooling of the type where children control their own curriculum and ways of learning. Please supply such a story if you have one, and please help spread the word to others. See the last post for further information.
*Some hyperlinks in these posts are automatically generated and may or may not link you to sites that are relevant. Author-generated links are distinguished from automatic ones by underlines.
 This model, which is now considered the standard cognitive model for ADHD, was initially proposed by Russell Barkley and his colleagues (1997), "Behavioral inhibition, sustained attention, and executive functions: Constructing a unified theory of ADHD," Psychological Bulletin, 121, 65-95.
 See, for example, Jensen & colleagues (1997), Journal of the American Academy of Child and Adolescent Psychiatry, 36, 1672-168.
 See Mayes & colleagues (2009), Medicating Children: ADHD and Pediatric Mental Health (Harvard University Press).
 K. Hopper & colleagues (2007). Recovery from schizophrenia: An international perspective (Oxford University Press).
 I have reviewed the evidence for this in P. Gray (2010), Psychology, 6th edition (Worth Publishers), pp 643-644.
 G. Ricaurte & colleagues (2005). "Amphetamine treatment similar to that used in the treatment of ADHD damages dopamine nerve endings in the striatum of adult nonhuman primates. The Journal of Pharmacology and Experimental Therapeutics, 315, 91-98.