What Does 'ADHD Is Real' Even Mean?

Following the Channel 4 documentary The Great ADHD Myth?, which aired in August this year, the Royal College of Psychiatrists issued a statement about it in which it described attention-deficit/hyperactivity disorder (ADHD) as a “well-established neurodevelopmental disorder,” the legitimacy of which "should not be questioned." An accompanying statement went further, stating, "Whatever you think about ADHD, its scientific basis is not in doubt."

These responses, and others, cite evidence of genetic and neurological differences, responses to stimulants, and institutional consensus as establishing the diagnosis of ADHD as “real” and beyond scientific doubt, treated as though they establish it as a distinct neurobiological entity, substantially genetic in origin. These are scientific claims that very much depend on evidence. The crucial question, then, is what the cited evidence actually establishes.

In a recent BMJ response that I co-authored with Joanna Moncrieff, Lucy Johnstone, and James Davies, we distinguished among the “experiential reality,” “institutional reality,” and “ontological reality” of "ADHD is real." These are very different claims, and they are used interchangeably in a way that misleads.

Three meanings of “ADHD is real”

First, "ADHD is real" is used to refer to the reality of the experiences and behaviours that are diagnosed as ADHD—difficulty with concentration, organisation, impulsivity, restlessness, and the demands of everyday life, sometimes in the extreme. This is ADHD's experiential reality. These experiences and behaviours are undoubtedly real.

The second meaning refers to the institutional reality of ADHD. It is a recognised psychiatric diagnosis, used by clinicians and healthcare systems and increasingly taken up by people as a way of understanding themselves. It is a diagnosis with material consequences and services organised around it, and, again, there is no doubt of its reality in this sense.

The third meaning of "ADHD is real" is that the diagnosis of ADHD has an ontological reality—that it identifies a discrete underlying neurodevelopmental disorder that explains the behaviours and experiences by which it is diagnosed. Much of the debate turns on this meaning. Unlike the first two meanings, this is not simply a factual claim but a scientific and conceptual hypothesis—one that remains thoroughly open to dispute, as I will show below.

Much confusion, polarisation—and, it must be said, misinformation—results from conflating these meanings. As we say in our BMJ response, it arises:

"From moving between these claims uncritically, particularly by conflating the first and third: the reality of the experiences and behaviours is treated as evidence that the diagnostic category and attached neurodevelopmental explanation are also real and true. This rhetorical move often curtails debate about the nature and causes of the problems we currently refer to as ADHD."

So, let's look at what the evidence actually shows us in relation to this third claim. I will focus here only on the two most important sources of evidence.

Where is the neurological disorder?

We often see claims that neuroimaging studies show that the brains of people diagnosed with ADHD are different. Neuroimaging studies, however, only identify (small) average differences between groups, while the relevant distributions substantially overlap, findings vary across studies, and many reported associations are shared with other diagnostic categories. In other words, they produce no single, consistent neurological finding in individuals diagnosed with ADHD, which can be illustrated with two examples. First, such group-level differences may be entirely absent in someone diagnosed with ADHD, yet present in someone who does not have the diagnosis. Second, the same differences may also be found in people given entirely different psychiatric diagnoses. We can see, then, that the findings themselves do not tell us anything specific about an "ADHD brain" or pattern of neurological functioning specific to people diagnosed with ADHD. It should be clear, therefore, that it is very misleading to suggest that these findings establish the neurodevelopmental status of the ADHD diagnosis.

Heritability is not genetic causation

Genetic evidence is often used in much the same way. ADHD is frequently described as “highly heritable,” and this is commonly presented—and understood—as evidence that the experiences and behaviours grouped underneath the diagnosis are largely caused by genes. But that is not what a heritability estimate means, and heritability findings cannot establish such a claim. Heritability estimates how much of the variation in a measured trait, within a particular population and under particular environmental conditions, is attributed to differences between individuals that are considered heritable. It neither tells us how much of an individual’s difficulties are caused by genes nor that there is any specific genetic mechanism. Furthermore, heritability can also change as environments change and does not, by itself, distinguish genetic effects from the developmental processes through which genes and environments interact. So, again, it should be clear that suggesting or implying that "ADHD is largely genetic" is very misleading.

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Diagnosis is not the alternative to neglect

Neither set of findings, then, establishes a discrete neurodevelopmental entity or specific causal mechanism. So, the third sense of "ADHD is real" is not substantiated. Description becomes explanation, while group-level associations become claims about what individuals "have." And this is where the problem arises. Rightful criticism of the ontological reality of ADHD is repeatedly presented as though it were equivalent to saying that people’s difficulties are imaginary or that they should be denied help, which is to conflate the first and third meanings outlined above. This is done by psychiatric professionals and institutions, which is deeply problematic, as people look to these institutions as authoritative sources of knowledge about what it means—and what it says—about them.

As we conclude our BMJ response:

“The public are being misinformed by psychiatric institutions and other organisations in claiming that the science is settled. The public deserves to know the real status of the scientific research and have access to alternative ideas and approaches to the problems conceptualised as ADHD."

As Nobel Prize-winning physicist Richard Feynman famously put it, “Science is the belief in the ignorance of experts."

Critiquing the diagnosis of ADHD is not suggesting that the experiences, behaviours, and impairments grouped under ADHD are unreal, trivial, or undeserving of support. It concerns the psychiatric explanation of these in terms of an underlying neurodevelopmental disorder, something that is not established by the evidence. Recognition and support do not depend on accepting a psychiatric explanation; both can be provided on the basis of assessed need. To insist that the status of ADHD is "beyond scientific doubt" is not only obviously unscientific but also serves to close down precisely the unanswered questions at the root of the issues we are seeing.