Researchers dispel myths on increased incidence of autism disorder

There has been a major increase in the number of children diagnosed with autistic spectrum disorders over the last two decades - the question is why? Researchers have found a sharp difference between the beliefs of ordinary people and medical experts about the reasons for the increased incidence of autism.

Expert consensus is that the rapid increase is a result of changes in diagnostic practice, but many lay people directly or indirectly affected by the disorder believe that the number of cases have increased in absolute terms. Many also believe that increasing incidence is the result of exposure to new environmental hazards and other effects of modern lifestyles.

A study carried out by researchers from the universities of Exeter and Bristol examined the ideas put forward in unsolicited correspondence to scientists carrying out research into the causes of autism. "Our study highlights the contrast between lay explanations of the increasing prevalence of autism and the consensus opinion of medical experts," says researcher Ginny Russell. "It also demonstrates the strength of lay belief that the rise is due to risks from modern technologies and changing lifestyles, showing a latent unease with these developments."

The researchers, from Egenis, a research centre at the University of Exeter, and the department of community based medicine at the University of Bristol, have published their findings in the journal Child: Care, Health and Development.

"There is no doubt that the reported prevalence of autistic spectrum disorders has increased spectacularly over the last 20 years," said Ms Russell. "Medical consensus is that the increase is not a 'real' increase in cases but is the result of the diagnosis being made more often.

"But our examination of letters and phone calls received by scientists carrying out research into the environmental causes of autism shows that, in the opinion of many people in contact with autistic children, it is not diagnosis but true incidence which has increased, and these people think that we should be investigating what factors have led to this increase. They believe that it goes hand in hand with lifestyle changes in the late 20th and early 21st century, changes which are causing autistic spectrum disorders to occur more often."

More than 40 different environmental factors were put forward as potential causes by correspondents, including foetal monitoring, vaccines, mobile phone radiation, and food additives.