The so-called “autism epidemic” is due to more children being diagnosed with less severe symptoms and not because more are being born with the disorder, according to an Australian study.
The findings, published in the international journal Autism Research, are the first evidence of a reduction over time in the behavioural severity of individuals diagnosed.
The reason behind a 20-fold rise in the prevalence of autism over the past 30 years has been a mystery.
Autism Spectrum Disorder is characterised by impairments in social interaction, verbal and nonverbal communication and by repetitive patterns of behaviour.
“The prevalence of autism is now thought to be at least 1% (in Australia),” says Professor Andrew Whitehouse, head of autism research at Telethon Kids and lead author of the study.
“But a question that has remained unanswered, is: What is behind the dramatic increase in the number of children being diagnosed with autism?
“Are there truly more kids with autism now than there were before, or is it more a case of us recognising more kids?”
Researchers examined the diagnostic information of 1,252 children diagnosed between 2000 and 2006, which are the years that saw the biggest increase in autism prevalence throughout Australia and the world.
Professor Whitehouse says the research show the majority of the increase in autism over this period was due to an increase in diagnosing children with less severe behaviours.
“In essence, there has been a clinical shift towards diagnosing children with less severe behavioural symptoms,” he says.
“Other research has shown these children would previously have either received a diagnosis of another condition such as language impairment, or not received any diagnosis at all.”
Professor Whitehouse says it’s wrong to infer that children with less severe symptoms do not have autism.
“Our understanding of the nature of autism has changed over time,” he says.
“We now recognise that the condition presents along a spectrum. It is critical that we are all aware of the full range of presentations, as well as the considerable strengths that individuals on the spectrum bring to our community.”
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