快猫短视频

RICHARD Miles will never forget the winter of 1989. The 34-year-old company director and his family spent that Christmas on the island of Jersey in the English Channel, where he had grown up. It was also then that he first noticed something was badly wrong with his 14-month-old son Robert. The bright, sociable child, who had already started talking, became drowsy and unsteady on his feet. Then he started bumping into furniture. Within weeks his language had dried up and he would no longer make eye contact. 鈥淚t was as if the lights went out,鈥� says Miles. His son was eventually diagnosed with autism.

Miles, who now campaigns for more research into autism, is convinced that his son is part of an autism epidemic. Ten years ago, he points out, Jersey had just three autistic children in special-needs education. It now has 69. Robert was one of a cluster of nine children on the island diagnosed around the same time.

Similar rises have been reported across the world, from Australia to the US, and from Denmark to China. Back in the 1970s, specialists would typically see four or five cases of autism in a population of 10,000. Today they routinely find 40, 50 or even 60 cases. Perhaps the starkest illustration of autism鈥檚 relentless rise comes from California. In 2003, the state authorities stunned the world when they announced that over the previous 16 years, the number of people receiving health or education services for autism had risen more than sixfold. The world鈥檚 media went into overdrive.

What could be causing so many children to lose their footing on a normal developmental trajectory and crash-land into the nightmare world of autism? The change has occurred too suddenly to be genetic in origin, which points to some environmental factor. But what? There is no shortage of suspects. In the UK, blame is often laid at the door of the combined measles, mumps and rubella (MMR) vaccine. In the US, mercury added to a range of childhood shots has been accused. Food allergies, viral infections, antibiotics and other prescription drugs have all been fingered, often by campaign groups run by mystified and angry parents. The problem is that none of these suggested causes has any solid scientific evidence to support it (see 鈥淭he usual suspects鈥�).

Perhaps there鈥檚 a simple explanation for this: there is no autism epidemic. On the face of it that sounds ridiculous 鈥� just look at the figures. But talk to almost any autism researcher and they will point to other explanations for the rise in numbers. Some say it鈥檚 still an open question, but others are adamant that the autism epidemic is a complete myth. And if the most recent research is anything to go by, they could be right. Studies designed to track the supposedly increasing prevalence of autism are coming to the conclusion that, in actual fact, there is no increase at all. 鈥淭here is no epidemic,鈥� says Brent Taylor, professor of community child health at University College London.

Autism is a developmental disorder sometimes noticeable from a few months of age but not usually diagnosed until a child is 3 or 4 years old. It is characterised by communication problems, difficulty in socialising and a lack of imagination (see 鈥淲hat is autism鈥�). It is not a single disorder, but comes in many forms, which merge into other disorders and eventually into 鈥渘ormality鈥�. There is no biochemical or genetic test, so diagnosis has to be made by observing behaviour. Autistic children also often have other medical conditions, such as hyperactivity, Tourette鈥檚 syndrome, anxiety and depression. The upshot is that 鈥渙ne person鈥檚 autism is not another person鈥檚 autism,鈥� says epidemiologist Jim Gurney of the University of Minnesota in Minneapolis.

In recognition of this ambiguity, autism is considered part of a continuum within a broader class of so-called 鈥減ervasive developmental disorders鈥� (PDDs) 鈥� basically any serious abnormality in a child鈥檚 development. Autism itself is divided into three categories: autistic disorder, Asperger鈥檚 syndrome (sometimes called 鈥渉igh-functioning autism鈥�), and pervasive developmental disorder-not otherwise specified (PDD-NOS), sometimes called mild or atypical autism. Together these three make up the autistic spectrum disorders.

鈥淐alifornian authorities stunned the world when they announced a sixfold rise in autism over the past 16 years鈥�

Confused? You鈥檙e not the only one. The difficulty of placing children with developmental problems on this spectrum has led to several major shifts in the way autism is diagnosed in the past 30 years. In the late 1970s, the autism label was kept for those with severe problems such as 鈥済ross language deficits鈥� and 鈥減ervasive lack of responsiveness鈥�. But since 1980 the diagnostic criteria have been revised five times, including the addition of PDD-NOS in 1987 and Asperger鈥檚 in 1994.

This massive broadening of the definition of autism, particularly at the milder end of the spectrum, is one of the main factors responsible for the rise in cases, says Eric Fombonne of McGill University in Montreal, Canada, a long-standing sceptic of the epidemic hypothesis. Tellingly, around three-quarters of all diagnoses of autism today are for Asperger鈥檚 and PDD-NOS, both of which are much less severe than the autism of old. 鈥淭here is no litmus test for who is autistic and who is not,鈥� says Tony Charman of the Institute of Child Health at University College London.

Changes in diagnostic criteria apart, there are other reasons to believe that autism is simply being diagnosed more often now than in the past. One is the 鈥�Rain Man effect鈥� 鈥� the huge increase in the public awareness of autism following the 1988 film starring Dustin Hoffman. Awareness has also increased massively among healthcare workers. 鈥淭wenty years ago there were maybe 10 autism specialists in the country. Now there are over 2000,鈥� says Taylor.

Another factor is that one of the stigmas of autism has largely disappeared. Until about 10 years ago a prominent idea was that autism was caused by an unloving 鈥渞efrigerator mother鈥�. Now it is a no-blame disease. 鈥淧arents are more willing to accept the label,鈥� says Taylor. One expert 快猫短视频 spoke to went as far as to describe autism as 鈥渢rendy鈥�.

Finally, while some parents still have to fight for help for their autistic children, far more services are now available. This has encouraged doctors to label borderline or ambiguous cases as autism 鈥� they know this is often the best way to get the child some help. It also makes autism an attractive diagnosis for parents. 鈥淚 hear stories of parents who are anxious to get a particular diagnosis if that is what is required to obtain the services their child needs,鈥� says Sydney Pettygrove, a paediatrician at the Arizona Health Sciences Center in Tucson. In the UK, says Simon Baron-Cohen of the Autism Research Centre at the University of Cambridge, 鈥渋n every town there are trained clinicians who can make a diagnosis.鈥�

It is hard to quantify these trends, but many epidemiologists now believe that they can account for the apparent rise in autism the general public and media take for granted. Proving it, however, is difficult 鈥� if not impossible. The main problem is that an epidemiological study carried out in the 1980s simply cannot be compared with one done last week. There will be so many differences in diagnostic procedures and in the willingness of doctors and parents to label a child autistic that comparisons are meaningless. 鈥淵ou can鈥檛 control for everything,鈥� says Charman.

And so attention has shifted to what epidemiologists sniffily refer to as 鈥渟ervice provider data鈥�, such as the California figures. Ever since 1973, the authorities there have been keeping records of the number of people receiving some kind of state help in connection with autism. In 2003, California鈥檚 Department of Developmental Services (DDS) announced a chilling figure that captured the world鈥檚 attention. In the 16 years to 2002, cases rose from 2778 to 20,377 (see Graph). Among autism campaigners these figures are often cited as incontrovertible and final proof of the existence of the autism epidemic.

But there are serious problems with this interpretation. First, the figures are raw numbers from public services, not a proper epidemiological study. Critics point out they are not corrected for changes in diagnostic criteria or for the growing awareness of autism.

鈥淧risons and institutions could be full of autistic adults labouring under wrong diagnoses such as schizophrenia鈥�

There is evidence, for example, that as the California autism numbers have risen, diagnoses of mental retardation have fallen. Researchers at Boston University School of Medicine in Massachusetts have found a similar pattern in the UK. This effect, dubbed 鈥渄iagnostic substitution鈥�, cannot explain all the increase but is one example of how diagnostic fashions can skew the data.

Another potential flaw is that the California figures don鈥檛 take into account the fact that the state鈥檚 population is growing rapidly. Between 1987 and 1999, the total population rose by nearly 20 per cent, and the age group 0 to 14 rose even more steeply, by 26 per cent.

As a result of these doubts and unknowns in the California figures, most epidemiologists refuse to draw firm conclusions from them. 鈥淭he report doesn鈥檛 change anything,鈥� says Charman. 鈥淚t鈥檚 not a systematic study.鈥� In fact, the preface of the most recent California report contains a health warning not to read too much into the numbers. 鈥淭he information should not be used to draw scientifically valid conclusions,鈥� it says.

Some researchers, notably Robert Byrd of the MIND Institute at the University of California, Davis, have attempted to correct for all the unknowns. In an analysis published on the state DDS website nearly three years ago, Byrd concluded that the rise is real. 鈥淎utism rates are increasing,鈥� he told 快猫短视频. Some scientists accept that Byrd鈥檚 analysis lays to rest the idea that population growth could have significantly swelled the figures. But his methods for investigating the other potential sources of bias have been heavily criticised, and tellingly, Byrd has not yet succeeded in getting his study published in a peer-reviewed journal. Until he does, it is hard to know how much weight to give his conclusions.

Perhaps the strongest case against the 鈥渂etter diagnosis鈥� theory is that, if true, there should be a 鈥渉idden hoard鈥� of autistic adults who were never properly diagnosed in childhood. To parent Richard Miles, this is compelling. 鈥淢y doctor cannot believe that he could have missed so many cases in the past,鈥� he says. But Taylor disagrees. As a former general practitioner, he says there are many children today diagnosed with autism who would not have been labelled as such in the past.

This view is difficult to substantiate, but in 2001 a team led by Helen Heussler of Nottingham University, UK, had a crack. They re-examined the data from a 1970 survey of 13,135 British children. The original survey found just five autistic children, but using modern diagnostic criteria Heussler鈥檚 team found a hidden hoard of 56. That鈥檚 over a tenfold rise in numbers, which puts the California figures in perspective. Heussler and her colleagues concluded that 鈥渆stimates from the early 1970s may have seriously underestimated the prevalence鈥�.

Lorna Wing, a veteran autism researcher at the Institute of Psychiatry in London, agrees. In the 1970s she spent a lot of time working with special-needs children in the London district of Camberwell. Wing reckons that at the time, fewer than 10 per cent of autistic children were correctly diagnosed. She also thinks that prisons and institutions are full of autistic adults labouring under wrong diagnoses such as treatment-resistant schizophrenia or ADHD.

Ultimately, however, it may be impossible to tell whether there has been a genuine rise in the incidence of autism over the past 30 years. 鈥淭here is no clear evidence that there has been an increase, but there鈥檚 no proof that there hasn鈥檛,鈥� says Charman. Even the arch-sceptic Fombonne accepts this. 鈥淲e must entertain the possibility,鈥� he says. 鈥淏ut we don鈥檛 have the evidence.鈥�

But researchers can answer another question: is the incidence of autism continuing to rise? There is a tried and tested method of tackling this sort of question. You carry out a large prevalence study among a particular age group, and then repeat it a few years later with a new set of individuals, in the same place and using exactly the same methods. Several such studies into autism are ongoing, notably one funded by the US Centers for Disease Control and Prevention in Atlanta, which will look at changes in incidence across 11 states.

One team, however, is ahead of the game. Back in July 1998, Fombonne and Suniti Chakrabarti of the Child Development Centre in Stafford, UK, started screening every child born in a four-year window (1992 to 1995) who lived in a defined area of Staffordshire, 15,500 children in total. As a result, they established baseline figures for autistic spectrum disorders 鈥� about 62 per 10,000. Then they did it again, in exactly the same place and exactly the same way, this time with all the children born between 1996 and 1998. In June this year, they reported that the prevalence of autism was unchanged (American Journal of Psychiatry, vol 162, page 1133). 鈥淭his study suggests that epidemic concerns are unfounded,鈥� concludes Fombonne.

Similar surveys need to be done in other parts of the world to rule out the possibility that there is something unusual about Staffordshire. And the Staffordshire result has failed to convince campaigners and parents, including Miles. But what is clear is that after the first direct test of whether autism is rising, it鈥檚 1-0 to the sceptics.

That doesn鈥檛 mean we should stop searching for the causes of autism. The disorder itself is real, and if researchers knew what was behind it much suffering could be averted. But the Staffordshire surveys do suggest that there is no environmental problem that is triggering autism in ever-greater numbers and which must be identified as a matter of urgency. That will not be much comfort to families with autistic children. But it should make everyone else feel a bit more secure.