Original post from Genetic Literacy Project
‘…………….By Arvind Suresh
The number of autism cases has skyrocketed in the past few decades. In the 1970s and 1980s, about 1 out of every 2,000 children had autism. Today, the Center for Disease Control and Prevention estimates that one in 150 8-year-olds in the United States has an autism spectrum disorder, or ASD. This expanded definition refers not only to autism but also to a collection of brain development disorders such as Asperger’s syndrome.
It’s been considered a medical puzzle. Mothers, and frankly all of us, are understandably concerned. Considering the numbers, it’s reasonable to ask: What’s causing the rise in cases.
Now researchers believe they know: Almost certainly, nothing. Most of the rise in autism is a statistical mirage.
That’s not the answer you’d find if the Internet is your medical guide. There are literally thousands of articles and hundreds of organizations blaming one thing or another, from vaccines, GMOs and pesticides to evenelectromagnetic fields, Wi-Fi signals, chemtrails and residential proximity to freeways. Scare headlines are everywhere. Posts like “How I Gave My Son Autism” tell stories of perfectly capable mothers blaming themselves for their child being diagnosed autistic.
Earlier this week on the Genetic Literacy Project we highlighted a claim that’s raging through cyberspace blaming autism’s rise on the herbicide glyphosate, which is frequently paired with GMO crops. According to an MIT computer scientist with no background in agriculture, genetics or epidemiology, half the country’s children will be born with autism by the mid 2020s because of the increased use of genetically modified crops. Articles carrying that claim registered millions of hits.
On the surface, some of these claims seem plausible. After all, the rise in the incidence of autism does track the rise in glyphosphate use–if you ignore its heavy usage for 20 years (since 1974) before GMOs were introduced (in 1994), when autism rates held steady.
But correlation is not causation. By cherry-picking the data, one could show that all of the alleged causes of autism, even the increase in chemtrails caused by soaring jet traffic, correlate with the rise in autism cases. As, in fact, does the rise in organic foods.
Because many of the reasons for the increased incidence are unknown, autism has become the defacto target for individuals and groups who have little else to point at. As much as the radical fringes of the organic food and everything-natural industries blame Big Ag and Big Pharma for the dramatic rise in autism, they are deftly making the most out of the situation monetarily as well.
So what does the latest evidence show? There now is intriguing evidence that there in fact has been no dramatic rise in autism after all. According to a just-released study, scientists at the Aarhus University, in Aarhus, Denmark assessed more than 670,000 children born between 1980 and 1991 in Denmark, following them from their birth until they were diagnosed with Autism Spectrum Disorder, died, emigrated or reached the end of the study period which was December 2011. Among other things, Denmark is renowned for its excellent national medical records system, which allowed them to conduct a study of this magnitude and over the extended time span. Among the population studied, 4,000 children were diagnosed as being along the autism spectrum and many of these diagnoses were made after 1995.
Look at what happened just before that detected increase. Tara Haelle reports in Forbes
In Denmark in particular, the diagnostic criteria for autism expanded in 1994 to include a spectrum of disorders with a broader list of symptoms, thereby widening the definition of autism. Then in 1995, national data tracking began to include diagnoses made from outpatient patient visits rather than just diagnoses of those admitted to a healthcare facility.
The exact same thing has happened in every country that has seen soaring autism rates–the definition of what constitutes autism was dramatically expanded in the early 1990s to embrace the catch-all term Autism Spectrum Disorder–correlating with when GMO usage, chemtrail rates, pesticide exposure and organic food sales began a sharp increase.
The researchers discovered that the change in diagnostic criteria taken together along with the diagnoses made outside of a healthcare facility accounted for as much as 60 percent of the increase in prevalence of autism spectrum disorders. The authors of the study conclude thus
Changes in reporting practices can account for most (60 percent) of the increase in the observed prevalence of ASDs in children born from 1980 through 1991 in Denmark. Hence, the study supports the argument that the apparent increase in ASDs in recent years is in large part attributable to changes in reporting practices.
Though this in itself doesn’t mean evidence of a lack of increase in the prevalence of autism, it does say very emphatically that the huge uptick in numbers of autistic children diagnosed have more to do with how we diagnose the condition than an actual increase.
The idea that increased diagnosis contributes to higher prevalence of a disease is not new at all. In fact it is quite common especially as new diagnostic techniques come into play and early screening programs are put in place by governments. This often leads to debates in the medical literature about whether increases in prevalence of disease are real or due to an increase in diagnosis. Prostate cancer is a common example –incidence for prostate cancer jumped over 100 percent from 1986 to 1992 which coincided with an aggressive expansion of the prostate cancer screening program based on the Prostate Specific Antigen (PSA) test which was approved by the FDA in 1986.
The result of the autism study, even if somewhat expected is still very important. The quality of Denmark’s health records and the size of the study make it unique –it makes the data extremely robust and reliable. So how do these results translate to the United States? We do have similarities in how the diagnosis has changed writes Tara Haelle in Forbes
The way autism is defined in the U.S. has changed dramatically since 1980, when it first appeared in the DSM-III as “Infantile Autism” and could only be diagnosed in children whose symptoms began before they were three years old. Autism spectrum disorders have expanded to include diagnosis without a specific age requirement beyond the “early developmental period” and without requiring significant language impairment in the recently revised DSM-5.
The vast majority of people diagnosed with autism spectrum disorders today would never have qualified under the 1980 classification, and no formal classification separate from schizophrenia existed before then. So it’s not surprising that numbers have increased in the U.S.
There are many possible causes why there is an increase in the prevalence of a disease. Apart from increased screening and changes in diagnostic criteria, factors like increased awareness will also come into play. As credible scientific efforts around the world continue to identify genetic and/or environmental causes behind autism, it is prudent to not be taken in by wild claims and give in to the fears spread by those who accept and promote pseudoscience. And no, the Wi-Fi in your house or the genetically modified foods you eat will not lead to your child becoming autistic.
Arvind Suresh is a science communicator and a former laboratory biologist. Follow him @suresh_arvind