Autism 'more common than previously thought'

Last updated at 00:05 14 July 2006


Autism disorders could affect one in 100 children in the UK, scientists said today.

A study found that childhood autism and related problems - collectively known as autism spectrum disorders (ASDs) - are far more common than previously thought.

Prior to the 1990s, experts estimated the rate of autism in Britain to be around four or five cases per 10,000 people.

Since then there have been indications that the true prevalence is much higher.

But whether this is due to a genuine increase in numbers of cases, or merely the result of labelling more children as autistic, is not known.

Autism is an umbrella term for a range of developmental disorders that impair a person's ability to interact socially and communicate.

They cover a "spectrum" ranging from severe cases of "classic" autism, through a variety of "pervasive developmental disorders", to much milder Asperger's syndrome.

Professor Gillian Baird, from Guy's and St Thomas's NHS Foundation Trust in London, examined rates of ASD in a group nine and 10-year-olds.

From a group of 57,000 children in South London, her team identified 255 already diagnosed as having autistic disorders and 1,515 judged to be possible undetected cases.

A randomly selected sub-group of 255 children were chosen for in-depth clinical assessment.

The prevalence of "classic" childhood autism was 39 per 10,000, and that of other ASDs 77 per 10,000. In total, autistic disorders affected 116 per 10,000 children.

The findings, published today in The Lancet medical journal, indicated that one in 100 British children may have some form of autism.

"Prevalence of autism and related ASDs is substantially higher than previously recognised," said Prof Baird. "Whether the increase is due to better ascertainment, broadening diagnostic criteria, or increased incidence is unclear.

"Services in health, education, and social care will need to recognise the needs of children with some form of ASD, who constitute 1% of the child population."

A number of theories have been put forward to explain the rising number of autistic children in the past decade.

Most controversial has been the suggested link with the measles, mumps and rubella triple vaccine, which put large numbers of parents off vaccinating their children.

Another suspect was thimerosal, a vaccine preservative containing mercury.

But both theories have been strongly refuted by research evidence. In particular, the continued increase in ASD incidence after the MMR jab was withdrawn in a district of Yokohama city, Japan, cast serious doubt on the vaccine claim.

Also writing in The Lancet, Dr Hiroshi Kurita, from the Zenkoku Ryoiku Sodan Centre in Tokyo, suggests that the recent surge in cases can reasonably be attributed to improved diagnosis.

"Such progress seems to have resulted in the identification of a greater number of high-functioning pervasive developmental disorders, which are harder to detect than those disorders with mental retardation because of their milder autistic symptoms." he wrote.

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