Psychology | Are Autism Cases Really On The Rise?

Autism Spectrum Disorder (ASD) has been a topic of increasing interest and concern in recent years. It isn’t just the fact that more individuals are being diagnosed with ASD; it's the per capita increase that seems to be trending globally. And it’s got everyone scratching their heads and asking: Why is this happening? And what’s causing it?

Autism On The Rise: What Does The Data Show?

The graph below is taken from US CDC data and represents an estimation of ASD prevalence in the US over time per 1,000 individuals. The trend clearly shows an increase in prevalence, but more than that, it doesn’t appear to be set to plateau anytime soon. Indeed, after 2016, the data shows an unprecedented increase, a trend that, generally speaking, is consistent globally.

Credit: CDC

Now, some corners of the media have taken this information and run with it without fully explaining the caveats of the data. This has unfortunately generated a whole host of conspiratorial theories and myths, particularly post-COVID and with the subsequent rise of the anti-vax movement.

After all, the average person could be forgiven for thinking that data, in and of itself, is an answer, but it’s not. Data needs to be contextualised alongside factors that may be disproportionately affecting it, and it is something that goes largely underreported because it is less sensational and more scientific. 

So, with that being said, what exactly is the context? 

Widening The Spectrum For Diagnosis

Globally, clinicians use two primary sources to generate a mental disorder diagnosis: the International Classification of Diseases (ICD), used worldwide, and the Diagnostic and Statistical Manual of Mental Disorders (DSM), used primarily in the U.S. but also supplementarily in other countries.

Both of these systems, in their latest updates, made significant changes to the diagnostic criteria of ASD by consolidating previously separate conditions such as Asperger's, Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS), and Autism Disorder into one umbrella spectrum. This means that following the changes to classification, ASD numbers are no longer the result of one condition but many.

And it’s a trend that can clearly be seen in the data. DSM-5, the update that created the umbrella spectrum, was published in mid-2013. As with all systems, there is a lag time between publication and implementation, which, according to healthcare providers, was expected to be around October 2015. This is about the same time you start seeing a sudden, disproportionate per capita increase, which isn’t helped by the inconsistency of retrospective changes to historic data to account for updates. In an ideal world, researchers would add the volume of cases for previously separate conditions to make the information more representative of the facts.

Improved Diagnostic Mechanisms

As a society, we are sometimes guilty of forgetting how different things were in the past. It’s worth bearing in mind that the conditions that make up the modern autism spectrum only started to be widely understood in the 1980s. While understanding did improve in the 2000s, the diagnostic mechanisms were still in the early stages. In fact, it’s only in the last decade that they have started to be refined, hence the continued updates of the DSM and ICD standards.

Nowadays, most first point of contact healthcare professionals, such as GPs, not only understand the condition but also have a specific roadmap for getting patients a diagnosis and then treatment. So, part of the sharp rise you’re seeing is a result of healthcare professionals becoming more efficient at identifying and testing for ASD.

It’s also likely you’ll see another per capita change relatively soon as AI and other medical-related technologies advance, allowing healthcare providers to develop a more interdisciplinary approach that’s likely to include genetic testing, analysis of biomarkers, and neuroimaging.

Awareness & Catch-Up Diagnoses

The stigma surrounding ASD has changed in part because of individuals like Elon Musk, who openly talks about his own Asperger's diagnosis. This, generally speaking, has meant individuals feel less of a need to mask their condition and are more likely to engage with healthcare professionals about their symptoms.

This has led to more people getting diagnosed later in life, but as mentioned previously, historic data isn’t often retrospectively changed to represent this. So, in some data sets, these late-life diagnoses are being logged as new cases rather than historical, creating an inflated representation of what’s actually happening.

Self-Diagnosis and Social Media

As a general rule, self-diagnosing on the internet is a bad idea. People who do so usually end up catastrophising, arriving at their GP with the firm belief they have the rarest of diseases, when in actuality it's a cold.

And thanks to social media, self-diagnosis of autism and ADHD is becoming more common, particularly on sites like TikTok, where ‘health influencers’ can offer to test you in 60 seconds or less.

This has caused problems in the NHS, leading to a number of prominent individuals, such as Professor Simon Wessely, former president of the Royal College of Psychiatrists, to state that we are at a stage of overdiagnosis and that growing levels of awareness are less likely to be beneficial. This is because a greater number of individuals with very mild tendencies are clogging up the system for those with serious symptoms, whilst at the same time watering down the perception of how severe ASD can be. It’s also been argued that these individuals with very mild tendencies are now starting to distort the data.

Now, that's not to say that all self-diagnosers may not have autism, but there is growing scientific evidence that the diagnostic mechanisms aren’t perfect. There is also the suggestion that miscategorisation is occurring as less specialised healthcare providers are confusing autistic tendencies with ASD. In reality, everyone has some degree of autistic tendency, even if they aren’t actually autistic. Difficulty communicating socially, disinterest in social interaction, difficulty dealing with change, and so on are very common sentiments surrounding the human condition. 

The truth is that people with genuine ASD have a distinctive physical brain morphology, usually consisting of an enlarged hippocampus, an amygdala that is either larger or smaller than average, different patterns of thickness in the cortex, and decreased brain tissue volumes in the cerebellum. There is also variance in synaptic density, grey matter volumes, and reduced neural pruning.

So, looking forward, the real question is, when testing for autism is performed less by behavioural models and more by biological models, how likely is it that the per capita number remains the same? And that, perhaps, is the only definitive way to determine if autism cases are actually on the rise.

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