Major new study casts doubt on the concept of 'ADHD'

Back in 2003 (before even Liberal England existed) I wrote an article for the mental health magazine OpenMind - Always on the Go - that was sceptical about the concept of 'attention deficit hyperactivity disorder' or ADHD.

This is a supposed mental health condition characterised by such symptoms as failing to do homework, fidgeting and being ‘always on the go’.

As I wrote back in 2003:

In the USA, at least 10 per cent of children – 5 or 6 million out of 50 million – are taking medication to treat ADHD; 90 per cent of them boys. In some classroom in prosperous New England states, as many as one boy in three can be on drugs.

Not only are the numbers diagnosed enormous, they are rising rapidly. The most commonly prescribed treatment for ADHD is methylphenidate, better known under its brand name Ritalin. Back in 1988, one million American children were taking it: in 1975 the figure was 150,000. 

The same trend can be seen this side of the Atlantic. Department of Health figures show that National Health Service prescriptions of Ritalin in England rose from 2,600 in 1992 to 186,000 in 2000.

That trend has continued ever since. This Daily Mail report from last year does not say whether its figures cover England or the whole UK, but the direction of travel is clear:

Prescriptions for Ritalin and similar medications for ADHD have risen by 70 per cent in the past five years, with more than 12,000 written out each week ... 

Department of Health figures show last year 661,500 prescriptions were written out for Ritalin and similar drugs such as Concerta – up from 382,000 in 2005.

Let's think of an experiment. If my sceptical view of ADHD - that the behaviours that constitute its symptoms are better regarded as childish (or boyish) high spirits and naughtiness, and that it is social change over recent decades  that has rendered them problematic - is correct, what would you expect if you compared the oldest and youngest children in the same school year?

I think you would expect the youngest children to be diagnosed with ADHD more often than the older children. And that is precisely what a major new study from Canada has found.

As CBC reports:

University of British Columbia researchers focused on 937,943 students who were six to 12 years old between Dec. 1, 1997, and Nov. 30, 2008 in a province where the cutoff age for entry to school is Dec. 31. The study, published in Monday's Canadian Medical Association Journal, found children born in December were 39 per cent more likely to be diagnosed and 48 per cent more likely to be treated with medication for ADHD, compared to children with a January birthday.

As a good Popperian I shall not claim that this proves I am right. But I can claim that an important test has failed to refute my hypothesis. Certainly, the size of the sample in this study is impressive.

It may be that ADHD is represents a coherent concept. It my be that the condition is caused by an as-yet-undiscovered abnormality of the brain. And it may be that this abnormality, for some unknown reason, is more common in children born in December than children born in January.

But I think Occam's razor suggests that the burden of proof is on those who uphold the concept of ADHD.