Do More Children Have Autism Now Than Before?

Diagnostic substitution

The expansion of diagnostic boundaries has meant individuals who would previously have been placed under a different “diagnostic banner” are now more likely to receive a primary diagnosis of autism. This is particularly true for the diagnoses of language disorders and intellectual disability, and the prevalence of these conditions has decreased over the past two decades as autism diagnoses have increased.

Methodological differences

As knowledge about autism has advanced, so have the techniques used to measure the prevalence of the condition. Early prevalence studies examined populations considered small by epidemiological standards (e.g. health districts), and used relatively crude diagnostic tools.

The modern method of screening whole populations (e.g. states or countries) using improved diagnostic assessments is likely to be more sensitive in identifying affected individuals.

Socio-cultural influences

Certain societal influences make it more likely for an individual to be diagnosed with autism today than in the past. These include:

• increased awareness and understanding of autism among parents and health professionals
• the formation of specific autism diagnostic teams
• a lessening in the stigma associated with a diagnosis (particularly, the dispelling of the myth that autism is caused by “cold parents”)
• the availability of governmental assistance specific to children with an autism diagnosis.

These potential explanations assume there has been no difference in the “true” rate of autism over the past 50 years; rather, what has changed is the way that we conceptualise and measure the condition.

But one should always be cautious about adopting a position based on null findings. It’s quite possible the true prevalence of autism is increasing, and we just haven’t yet identified the cause.

One potential candidate is the increase in the survival of extremely premature infants. While recent findings suggest these infants are at increased risk of autism, research in this area is at too early a stage to make conclusive statements.

What we can conclude from research to date is that there is no single environmental factor we know of that has substantially contributed to the increase in autism diagnoses.

Research into Autism Spectrum Disorders is at an exciting stage, where we can examine how genes and the environment combine to cause this condition.

If the next 20 years of research is half as fruitful as the previous 20, it’s a good bet that we will get to the bottom of the supposed “autism epidemic”.

This article was originally published at The Conversation.
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