Verified by 
Key points
- What we call ADHD is, in most cases, just one end of a bell curve describing normal executive function.
- Executive function is centrally important to many aspects of day-to-day functioning.
- Modern society increasingly requires high executive function to cope with day-to-day demands.
- People with less acute executive function find themselves disadvantaged, and may meet criteria for a disorder.
Everyone arriving for an assessment in my youth psychiatry clinic1 seems to have ADHD these days. Well, not everyone, but sometimes it really feels that way.
Not coincidentally, in the last few years, there has also been an explosion of interest in the self-diagnosis of ADHD on the internet and social media, some of it serious and some of it excessive and misinformed.
What’s going on?
A Continuum
Part of the confusion stems from how ADHD is described and categorized as a “disorder.” Most textbooks or official websites state that ADHD is a neurodevelopmental disorder, portraying it as an abnormal brain condition with specific causes.
For example, the CDC states:
ADHD is one of the most common neurodevelopmental disorders of childhood […] Scientists are studying cause(s) and risk factors in an effort to find better ways to manage and reduce the chances of a person having ADHD. The cause(s) and risk factors for ADHD are unknown, but current research shows that genetics plays an important role. Recent studies link genetic factors with ADHD.
The phrasing of such explanations creates the impression that ADHD is a “thing” that you either “have” or don’t have. This inevitably leads to endless debate about whether it's a “real thing” and whether a particular individual really “has” the condition or not.
This is entirely the wrong way to think about it.
What we call ADHD is, in most cases, just one end of a continuum (described by a bell curve) of normal executive function–a set of cognitive processes and mental skills that help an individual plan, monitor, and successfully execute their goals.2 It’s been known for a long time that ADHD is not only a deficit of attention. Attentional control is just one of several executive functions, though an important one. Each of us falls somewhere along that bell curve of executive function (EF), having varying degrees of intensity of EF–just as with most human traits (analogous to the IQ bell curve).3 People meeting the criteria for a diagnosis of ADHD are (in most cases) simply those whose EF is further toward the left end of that bell curve.4
Despite the language of the textbooks and official websites implying that ADHD is a clearly defined, well-demarcated disorder, most experts if pressed, would no doubt agree that ADHD is almost always on a continuum with normality. There is a lack of discontinuity–a lack of a clear threshold–between those who “have” or “do not have” ADHD when you look at the phenomenology, the genetics, the neuropsychological findings, neuroimaging findings, and effects of stimulant medications.
A Fuzzy and Shifting Threshold for Diagnosis
The fact that there is no fixed cut-off or threshold for the diagnosis means that ADHD is not a categorical yes/no diagnosis. It is a matter of degree.5 Someone whose difficulties with EF cause significant impairment in several aspects of day-to-day functioning might meet the criteria to be diagnosed with ADHD. The diagnosis is an inexact process based on a clinical impression–not something determined by objective “testing” or measurement.
It is also unavoidably influenced by the sociocultural context in which the individual is expected to function. Modern developed countries require people to have the ability to sustain high levels of focus, organization, time management, and planning, for successful functioning in many types of activities. These requirements have been steadily increasing as societies have become increasingly complex, specialized, and productive.
The increased performance demands of modern societies have almost certainly contributed to the increased likelihood of acquiring a diagnosis of ADHD. The structure of schools and many occupations favors individuals who are more able to sustain effortful focus and attention to detail in low-stimulation tasks requiring quiet patience, persistence, organization, self-discipline, and the ability to work towards delayed or abstract rewards. The environment created by modern societies bears little resemblance to the ancestral environment in which our species evolved for most of its history–an environment that would have equally favored both sides of the EF bell curve.
With modern societies increasingly requiring and favoring people with high EF, people with less acute EF (i.e., those toward the left-hand side of the EF bell curve) increasingly find themselves disadvantaged. Those who are further still to the left end of that curve may meet the criteria for ADHD–those individuals can, for practical purposes, be considered to have a disorder.
It's as if we’ve constructed a society designed for tall people, one in which many things are out of reach for short people, such that shorter people have become relatively disadvantaged. In this imaginary society, short people would have such difficulty navigating day-to-day living that, for practical purposes, they would be considered to have a “height deficit disorder.”6
Caution Not to Label Too Many People With a Disorder
Understanding ADHD this way goes a long way toward explaining and resolving the debate about overdiagnosis. (Another big part of the explanation is, of course, the internet and social media, which have contributed to increasing self-diagnosis. Pharmaceutical marketing over the decades is yet another factor that has contributed to increased diagnosis).7
While it is helpful to understand that a relative weakness in EF is a common disadvantage in our society, we should be cautious not to casually label everyone with such weakness as having a “disorder.” For any normally distributed trait (i.e., a trait defined by a bell curve), 50 percent of the population is by definition below average for that trait. Obviously, nobody would suggest that half the population suffers from a “disorder.”
Nor should we define, say, 20-25 percent of the population as having a disorder. Applying DSM-5 criteria for ADHD generally identifies 5-10 percent of children and adolescents as having the disorder, and a somewhat lower percentage of adults (though, the identified prevalence of adults with ADHD has generally lagged that of children and adolescents, probably mostly due to under-recognition in adults). Thus, in a class of 30 students, an ADHD diagnosis should only really be applicable to the one to three students with the weakest EF.
Receiving an “official” diagnosis from a qualified and experienced clinician is important for things like academic accommodations and medication prescriptions.8
Stimulants
We should also reconceptualize how we think and talk about medications for ADHD. Perhaps we should stop referring to these as “treatments,” which implies that ADHD is an illness or disease, and understand that these medications are simply performance-enhancers. Most medications for ADHD are stimulants. That puts them in the same category as caffeine, but stronger and more effective.9
Just like caffeine, they work rapidly; their effects last for several hours and then wear off. They can be taken on an as-needed basis–when requiring increased focus, organization, and motivation for cognitively effortful tasks. (They can be taken daily, but they don’t have to be.) At the risk of over-simplification, stimulants temporarily increase the internal stimulation in a brain that is constitutionally a little lower in its natural state of internal stimulation–a brain that is more dependent on external sources of stimulation.
A more internally stimulated brain is a more focused brain–one that is more easily “satisfied” with quiet and otherwise “boring” activities.10 This variation in the natural level of internal stimulation of brains is just another way of describing the human neurodiversity we are talking about–a diversity that would have been very well adapted to the Paleolithic environment in which our species evolved.
A Much Wider Issue
In summary, ADHD is a real phenomenon, but we’ve misunderstood it by thinking of it in narrow categorical terms as a specific disorder–one that some people “have” and the rest of us don’t. (The name ADHD is also misleading.)11 It is, for practical purposes, just one end of a continuum of normal executive function. EF is fundamental to goal-directed behavior and self-control. We all have varying degrees of proficiency in EF. Relative weakness of EF is a very common and fundamental disadvantage in modern society.
Whether or not it is to such a degree as to warrant a diagnosis of a disorder (“ADHD”), the relative weakness of executive function nevertheless contributes to considerable difficulties in day-to-day functioning and self-regulation for a huge swath of the population.12
References
1. I work in a busy clinic in a major teaching hospital. Youth and young adults form a large part of my practice.
2. There is debate about the extent to which ADHD is purely a problem of weak executive function. The two are not identical, but they overlap so greatly as to be practically the same thing in most cases. There are of course other causes of deficits of EF besides ADHD, many of which involve more than mere neurodiversity: some causes of deficits of EF are neurodevelopmental, some neurodegenerative, and some caused by acquired brain injury or illness.
3. This is just an analogy; being high or low on IQ does not necessarily correlate with being high or low on EF.
[Click 'More' to view footnotes 4-12].
4. There are exceptions: not all cases meeting criteria for ADHD can be considered merely to be cases of “neurodiversity” on a continuum with normality. Some severe cases of ADHD, comprising a relatively small proportion of all people with ADHD, are caused by specific pathological conditions. One such cause is fetal alcohol syndrome.
5. Actually, this is true of most mental disorders.
6. The analogy can be taken further: most short people are short merely because of the way normal genes affecting height get "shuffled and dealt" to each individual before they are born (environmental factors also play a role). But small numbers of people actually have true genetic / chromosomal abnormalities causing extreme shortness – dwarfism (achondroplasia). Similarly with IQ and intellectual disabilities. So too, there are a few severe cases of ADHD that are caused by specific pathological conditions, like the example of fetal alcohol syndrome given above.
7. An additional reason for the increase in people seeking professional help for ADHD-related difficulties in the last couple of years (as of the time of writing, in 2022) has been the pandemic, as many people with relatively weaker EF and short attention spans were derailed by the loss of external structure and routine, and found online learning or online meetings boring and tedious.
8. An “official” diagnosis is also subjectively important to many individuals, who might otherwise have labelled themselves “lazy,” to provide validation that they have a “real” or legitimate disability.
9. The chemical action of these medications is not exactly the same as caffeine, but pointing out the broad similarity is helpful when explaining in simple terms how they work and what to expect from them.
10. One of the main chemical effects of stimulants is to increase dopamine, which is one of the brain’s most important mediators of attention and behavioral reinforcement.
11. The name ADHD (technically: AD/HD) is unfortunate, in that it seems to imply that the problem is purely one of attention span. The understanding that it is a problem of EF came later. Another source of confusion is that many people misunderstand it to mean that a person who meets criteria for ADHD cannot focus on anything, whereas in fact it is a difficulty maintaining effortful focus for unstimulating tasks. Also, the “H” (hyperactivity) only applies to some people, more so male children.
12. It also frequently plays a contributing role in other mental health problems and dysfunctions. e.g., anxiety, addictions, anger management problems, BPD traits, among others.
