Medium is a fascinating place, with a plethora of diverse opinions clashing and whirling in a wonderful maelstrom of words that is matched in few other areas of the internet. You can see gun lovers writing about shooting their AR-15s alongside the gun control advocates telling the world that we should melt them down. You get gym freaks arguing for the perfect abs next to the fat acceptance movement telling you that your body is beautiful no matter what.
And sometimes, you get people writing things that are just demonstrably untrue.
Enter: the commonly-held belief that we are experiencing a massive epidemic of autism.
There are a number of issues with this idea. It’s partly objectionable because of the way in which it dehumanizes those with a diagnosis. If anyone were to describe my learning issues as an ‘epidemic’ I would be extremely upset*.
But more importantly, inherent in this argument is the supposed ‘fact’ that autism rates are skyrocketing.
It turns out, that’s not true at all.
History Of Autism
To talk about autism rates, it’s important that we start at the beginning. A lot of people are still not entirely sure what ‘autism’ actually is, which is partly because — like many mental health issues — the history is murky, unclear, and highly stigmatized.
‘Autism’ as a medical term was first used in the early 20th century to describe how people suffering from schizophrenia were often withdrawn into the self — autism comes from the Greek “autos” meaning “self”. Fast forward 40 years, and you find that several psychiatrists are beginning to use the term to categorize a range of childhood disorders that they describe as characterized by a lack of interaction with other people. A few decades later, the term autism was popularized and became more widely known as a diagnosis after it was more narrowly defined, allowing doctors to start using it in their practice. In the last two decades psychiatrists have again expanded the term to include a wide range of different conditions, using the term “autism spectrum disorders” (ASDs). This has taken sub-diagnoses such as Asperger’s disorder, which was once very common, and clumped them all together under a single broad label.
All of this is important, because when we talk about an “autism epidemic” you have to remember that “autism” isn’t a single, discrete disorder. There are likely hundreds of factors that make ASDs occur, unlike say tuberculosis which is caused by a specific bacteria and that can be readily identified in a lab.
What we can say is that the rate of autism, however you define it, appears to be increasing. Quickly.
However, looking at these figures — what’s known as the ‘crude prevalence’ in epidemiological terms — can be very misleading.
What does this actually mean?
Diagnosis Is Tricky
There’s a huge issue with looking at crude prevalence rates of a disorder like autism. Basically, as the diagnosis shifts, more or less people fall under the category. Imagine that the term “autism” is an umbrella. If you make the umbrella bigger — widening the diagnostic category — more people will be huddled together underneath it. There are often good reasons for this, such as increasing access to services for similar disorders, but the end result is that you see more people with a diagnosis of a disease.
A great example of how this umbrella can work is diabetes. When glycated haemoglobin (HbA1c) testing improved, allowing doctors to better examine people’s blood sugar averages, there were changes in how we categorize diabetes. This led to a large number of people being diagnosed with the disease. None of these people actually had any differences in their health — they didn’t get sicker or change in any way — but the new definition of diabetes caught them under its umbrella. Similarly, when psychiatrists expanded the definition of autism in the early noughties by eliminating subtypes and collating a number of disorders under the term ASD, the rate of autism skyrocketed.
Does this mean that more people have autism now than in the 90s? Not necessarily. It could just be that more people are being diagnosed as autistic who previously would’ve been undiagnosed or possibly diagnosed with something different.
And it appears that’s exactly what happened.
A team of scientists from the University of Queensland in Australia were interested to know what the actual increase in autism was, once you excluded all the changes in diagnosis over the last 30 years. They looked at every study across the world that measured the number of people who had autism between 1990 and 2010, and looked at the number of people who were diagnosed with specific, similar symptoms. So rather than basing their analysis on diagnosis, which we know has changed, they looked at what symptoms people actually had.
And contrary to all those scary stories about the autism epidemic, they found nothing.
No change in autism rates.
No “epidemic” of any kind.
It turns out, when you exclude changes in diagnosis and regional variation, the rate of autism in the general population remains pretty fixed at 0.75%. It’s certainly an issue — the other main finding of this study is that we need to improve the services that cater to autistic people — but it’s hardly the scare story you often see online.
And this is not really a surprise. Despite the fear-mongering by many anti-vaccine crusaders, there is no evidence whatsoever that autism is linked to vaccines. Autism is likely caused by a range of genetic and environmental factors, but since it’s such a broad category we really aren’t sure yet what’s happening.
Bottom line? There is no autism epidemic. The apparent increase in the number of people being diagnosed as autistic is simply down to changes in the diagnosis, not more people being sick.
And vaccines save lives.
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*To clarify, I am not autistic but have two diagnosed learning disorders