Debunking environmental causes of autism

Dr Michael Fitzpatrick (pictured) looks at the various theories that have been put forward for the rising number of autism cases and finds there is no epidemic

The concept of an autism epidemic is a key belief of those who attribute autism to environmental causes such as vaccines. But if there is no real epidemic, we might just have to admit that nobody is to blame.

The notion has an intuitive appeal to parents of children with autism, who may have known little about autism before their child’s diagnosis. They generally grew up in the 1970s and 1980s when there was little public recognition of autism they had children in the 1990s and 2000s when awareness grew dramatically. Parents of children with autism soon began to meet each other.

Having lived for years without knowing a family affected by autism, suddenly they know many within the same community in which they have always lived. Parents draw the conclusion that their perception of an increased number of people with autism reflects a real increase. But is there really an epidemic?

Earlier this year a study was published showing that the prevalence of autism in California had increased steadily since 1995. This dry epidemiological research was big news because campaigners who claimed that vaccines containing the mercury-based preservative thimerosal were responsible for an autism epidemic had anticipated a decline in autism rates after the elimination of mercury-containing vaccines.

Increase in numbers

In 1999 state authorities noted a dramatic increase in the number of children being registered for services as autistic: a rise of 273% over the preceding decade. With advocates of a link between vaccines and autism (and their lawyers) claiming the California figures confirmed their theories, public health authorities panicked and removed mercury-containing vaccines as a precautionary measure.

If mercury were causing the epidemic, rates should have fallen after 2004 (when children who received mercury-free vaccines would start to be diagnosed with autism). This was the dog that failed to bark in the night: the California graph showed a steadily rising gradient, providing strong evidence that, whatever was causing the increased prevalence of autism, it was not thimerosal.

Of course, scientific evidence contradicting the alleged vaccine-autism link has not deterred its advocates from dogmatically pursuing their claims. While some in California bluster about atmospheric mercury pollution wafting over the Pacific from coal fires in China, others continue to blame MMR.

In his book Unstrange Minds, anthropologist Richard Grinker summarises the factors that have led to an increased prevalence of autism. These include:

Better awareness and better diagnosis of autism.

Children are being diagnosed earlier than ever.

Autism and schizophrenia are no longer conflated.

The concept of autism has broadened.

Autism is replacing the label “mental retardation”.

For Grinker, “the newer, higher, more accurate statistics on autism” are “a sign that we are finally seeing and appreciating a kind of human difference that we once turned away from and that many other cultures still hide away in their homes or institutions or denigrate as bizarre”. While he sympathises with the quest for some environmental cause for the increase in cases of autism he believes that it is misguided.

As he concludes: “We cannot find real solutions if we’re basing our ideas on false premises and bad science.”

Dr Michael Fitzpatrick is a GP in the London Borough of Hackney

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