''Don't call me that word!" says a furious six-year-old, sitting between worried parents and NHS psychologists in a drab, suburban family centre. She is in the middle of what is becoming a familiar scene in modern Britain: the ritual of the official diagnosis of Asperger's syndrome, or mild autism. It's the word Asperger's that has been whispered between her parents and professionals in her hearing once too often. Some specialists in this complex area of paediatrics believe that, if a child challenges the diagnosis, it is wrong by definition.
Non-professionals might also wonder why a child communicative and intuitive enough to recognise the word might ever be thought autistic, or anything like it. But in this case the diagnosis stood, as it does in so many others now - maybe not fully fledged autism, but "Asperger's" or "autistic spectrum".
Autism was first diagnosed in 1943; the word itself, coined in 1908, was used to describe children who were self-absorbed and unable to interact socially. The field has become particularly complex and controversial over the past decade, partly following the translation into English of work by Hans Asperger, who linked clumsiness in children to autism in the 1940s, and partly because autism has been linked to other questions, including the hotly disputed claim that the childhood jabs against measles, mumps and rubella (known as MMR) might trigger the condition.
The figures are certainly frightening. There are now half a million people in the UK said to be suffering from autism, up 1,000 per cent among children in the space of ten years. That's one in 86 primary schoolchildren in England and Wales, and one in 121 in Scotland - enough to prompt a column in the Guardian by an agonised mother and a series of TV documentaries.
You can terrify people with percentages, and in the United States you will find claims on the internet of staggering 62,000 per cent rises in Illinois over the same period, and credulity-testing four-figure percentage rises in states such as Ohio and Nebraska. Actually, 1992-93 was the first time researchers collected figures in the US, so they are open to challenge. None the less, such figures appear on campaign websites, fanning the flames of a global autism panic. A recent study by the Royal Free Hospital in London cast doubt on whether there has been any rise at all, suggesting that the statistics simply reflect wider medical recognition of autism. Following publication of the study, Professor Priscilla Alderson, an expert in childhood studies at London's Institute of Education, claimed that the rise was about psychologists trying to "make a quick buck", and that symptoms would disappear if children were allowed out of the house a little more.
This may be true, yet perhaps what is most interesting is what the enthusiasm for diagnosing autism says of our fears about child behaviour. Why has a condition, so distressing for parents that doctors, until recently, might delay using the dreaded word for years, suddenly become so overwhelmingly "popular"? Why are parents so keen to have the diagnosis and psychologists and doctors so keen to oblige?
The question is behind not just the MMR debate, but also the deployment of scarce education resources, with the education authorities under pressure to provide for growing numbers of the mildly autistic. One answer may be our inability to deal with what was once called naughtiness - or even mild oddness. This is not to say that MMR jabs are necessarily innocent, or that autism isn't immensely distressing. It can tear a family apart when children shut down and withdraw from the world. Previous generations struggled over this mystery malfunction, but there is still neither a foolproof solution nor a clear cause.
Yet an afternoon at a family centre - with professionals fresh from courses on autism, doling diagnoses out to grateful and worried parents - might also make you wonder about the way we love to label and count the things we fear most. "It's trendy," one NHS child psychologist told me. "It's something that a lot of professionals have at the forefront of their minds. You find consultant clinicians are going to conferences on autism. Then if a child doesn't make eye contact with them, they think they're autistic."
Standing up against enthusiasm for diagnosing autism can blight a promising career - especially since the Department for Education and Skills allocated £25m to train professionals who can diagnose the condition early. Then there is Autism Awareness Week every May, making it hard to resist the wave. But there are other things going on as well. First, the whole idea of Asperger's syndrome, or "autistic spectrum disorder", may be one reason for the rising figures. You can't see it under a microscope - Asperger's is just a collection of symptoms - but that makes it very much easier to diagnose autism.
Second, the precious piece of paper with an official diagnosis can unlock a range of extra educational resources - the pre-school home visiting service, one-to-one teaching at a nursery, special language therapy and support for parents, not to mention special support at school. The Centre for the Economics of Mental Health says the lifetime cost to the public purse is about £2.4m per child. Even having a child with Asperger's makes parents eligible for respite care, plus individual support in school.
And third, parents are often enormously relieved to find that their child is not outrageously naughty - which might be their fault - but, instead, suffers from some kind of syndrome.
"Autism frames behaviour in a way that is tolerable to parents," says one sceptic, Craig Newnes, director of psychological therapies for Shropshire's Community and Mental Health Services NHS Trust. If doctors don't diagnose Asperger's, they have to look at relations inside the child's family to explain why they are so uncommunicative - and some families avoid that at all costs.
Since autism was first described, diagnosis has been problematic. There used to be 11 tests for it but, to be diagnosed, a child would have to fulfil only five of them. Two children with completely different symptoms could both officially be autistic. The situation is even worse with Asperger's. The official criteria of 1991 list six categories, and all six have to be ticked before a diagnosis of Asperger's can be given - but they can be ticked for completely different oddities. If you examine the list, you might conclude that we are surrounded by people within the autistic spectrum.
"Imposition of routines and interests", for example, or "lack of desire to interact with peers" or "clumsiness" could describe many of us. "Formal, pedantic language", "peculiar stiff gaze", or "absorbing interest more rote than meaning" could describe many in the current cabinet, or some psychiatrists. There lies the problem. Modern society, and particularly those who rule us, display many traits of Asperger's - yet somehow we see them only in children.
The Cambridge psychology professor Simon Baron-Cohen recently published the theory that Einstein and Newton both had Asperger's, basing his argument on the grounds that they were obsessive and didn't like small talk. The truth is, we are increasingly agonised and confused by "bad behaviour" - especially in young people. We feel powerless in the face of it and prefer to label it as a syndrome that might somehow, some time, be susceptible to a pharmacological fix.
The "discovery" of autism has a parallel in "attention deficit hyperactivity disorder" (ADHD), which is now said to affect one in ten children in the UK, with 345,000 prescribed the drug Ritalin - even children as young as 18 months. Like autism, ADHD is a collection of related symptoms which could apply at various times to almost all normal children: fidgeting, distractedness, forgetfulness, impulsiveness, "babbling about nothing".
Why this explosion of hyperactivity? A strong case has been made for it being related to food additives, but the widespread diagnosis is also partly the result of heavy marketing of the disorder by drugs companies. Even more importantly, agonised parents prefer a medical label for what once would just have been termed bad behaviour.
In fact, the worse children behave - and they can behave appallingly - the more society prefers to label and drug them, rather than face up to causes that might be nearer to home. As a result, four million American schoolchildren are dosed daily by the school nurse with Ritalin, often on the advice of teachers who want their pupils less argumentative.
"How has it come to pass," asks the Washington writer Mary Eberstadt, "that in fin-de-siecle America, where every child from pre-school onward can recite the 'anti-drug' catechism by heart, millions of middle- and upper-middle-class children are being legally drugged with a substance so similar to cocaine that, as one journalist accurately summarised the science, 'it takes a chemist to know the difference'?"
There is a conspiracy theory here: in the 1980s, drugs companies increased awareness of depression - which affected a tiny proportion of the UK population a generation ago - as a way of paving the way for drugs such as Prozac (the 1970s drug of choice was Valium). They did the same for ADHD in the 1990s, with awareness-raising seminars and expert papers. Are autism and Asperger's facing the same treatment now? Will the Asperger's drug be unveiled in a few years' time, to a ready and enthusiastic market?
I can only suggest that when it is, we do not pay too much attention to the statistics. Because we count what we fear the most as a society, and - when we are really scared - the figures rise.
David Boyle is the author of Authenticity: brands, fakes spin and the lust for real life (Flamingo, £12.99)