There is no “true” prevalence of ADHD

ADHD is back in the news, with more CDC data from the U.S. revealing that 11% of 4-17 year olds have an ADHD diagnosis, with 6% taking medication. From a UK perspective, these are striking figures, given that our diagnosis rates are more like 1-2%, and voices have been raised condemning over-diagnosis. Others allege that we are treating a social problem with drugs. Rather surprisingly, there are also researchers who contend that 11% approaches the condition’s true prevalence, which is if anything higher.
So both sides of the argument rely on there being a right answer to the question of ADHD’s true prevalence. But I don’t think there is a single true prevalence, so the argument cannot be settled in this way.
I’ll try to explain. ADHD is a developmental disorder. This means that it consists in a relative failure of certain developmental skills to develop. In this case the skills can be thought of as behavioral inhibition and sustaining attention. Like all developmental skills, these lie on a more or less normal distribution (the familiar bell curve shown below). For convenience, you can think of a single variable. In clinic, I explain this as having a fizzy brain, with too many ideas and impulses for you to see, think or act clearly. This property of fizziness is distributed across the population, with some people having still minds, others sparkling; these children fizz like an alka-seltzer.

The fizzy distribution

It’s important to point out here that one’s position on this distribution seems largely a question of biology, so there is, inescapably, a phenomenon here that needs addressing.
We’re all on this curve, somewhere, and the question is where one draws a line between the normal range and a disorder.
The trouble is, drawing the line at any point of this distribution, be it the top 10% or 1%, seems arbitrary in itself, unless it’s linked to impairment.
However, the link between a child’s position on this curve, and how much functional impairment they suffer, is not straightforward. Some families, and some schools, cope admirably with quite striking degrees of fizziness, while others do not. My experience is that families suffering other stresses, for instance poverty, violence and mental health issues, lack the capacity to cope, and so present to doctors with rather lower levels of fizz. Equally, an increasing emphasis on narrow academic measures of performance erode schools’ willingness to accommodate these children’s needs.
This phenomenon may in part account for the emerging social gradient in ADHD diagnosis, without contradicting the existing research suggesting strong biological determinants for neurological fizziness.
So what are the implications of this for diagnosis? Firstly, we should not rely solely on the child’s position on the fizziness curve for diagnosis, however tempting that printout from the questionnaire might seem. We need to identify pervasive functional impairment for this child, and convincingly attribute this impairment to their fizziness. By doing this we will, almost incidentally, keep diagnosis rates under control, as I have explained before.
What if the impairment isn’t pervasive (occurring across multiple settings, usually home and school), or the difficulties are only partly due the fizziness? I would say, change the environment where the problem occurs first. Support families; financially, emotionally and in their parenting skills. Support schools with training and consultation, and if necessary, politely remind them of their obligations. The need to do this, of course, means that part of running an ADHD service involves a public health function, making as many local classrooms and living rooms as friendly to these children’s poor attention and hyperactive behaviour as possible.
So while fizziness is a biological fact , ADHD is a society’s way off selecting off those who would benefit from particular attention by adding ‘disorder’ to their attention and hyperactivity problems. By ‘particular attention’, I do not mean drugs, except in severe attributable impairment or when other interventions have not worked. Of course it is not society that makes the diagnosis, but the more tolerant schools and parents can be of these wonderful, maddening children, the less the diagnosis will be needed to help individuals.
So when ADHD diagnosis rates get out of control, it’s not the kids who are sick; it’s us.


One thought on “There is no “true” prevalence of ADHD

  1. Pingback: Links 21 – 28/12/13 | Alastair's Adversaria

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