Thinking about autism has evolved.

Just three decades ago, autism was a relatively rare and clearly defined condition, diagnosed in people with limited verbal language and highly repetitive behaviour.

Today, autism is diagnosed along a spectrum of a wide range of abilities, from people who may require 24-hour care to those able to live independently.

Around 290,900 Australians are diagnosed with autism, a 42% increase from an estimated 205,200 in 2018.

For many people and their families, this has been an overwhelmingly positive change that has meant recognition of difference, and access to support they previously didn’t have.

But expanding the diagnostic boundaries of autism has also had unintended consequences. Are we leaving those with the most profound disability behind?

An expanding definition

Few diagnoses have broadened their diagnostic boundaries as much or as quickly as autism. In the space of a generation, autism went from a narrowly defined clinical condition to one of the most expansive categories in medicine. We now understand someone can be autistic without having an intellectual disability or significant language difficulties.

Today, autism is diagnosed based on differences in social communication and restricted or repetitive behaviours that are significant enough to affect everyday functioning.

At one end of the spectrum are people who may live independently but experience difficulties with social interaction, managing changes and sensory sensitivities.

At the other end are those with profound disability. They may have minimal spoken language, intellectual disability and require lifelong, around-the-clock support.

While there is broad international agreement about the core features of autism, the boundaries of the diagnosis continue to evolve. This means more people meet the threshold for diagnosis.

For example, there is evidence that some children in the 1990s who may have been described as “socially awkward” – but had autism specifically ruled out as a diagnosis – would now meet modern diagnostic criteria.

Autism can be a difference – and a disability

For many people, this expanded definition of autism has been positive.

In addition to better access to support, diagnosis can give some people a way of thinking about and understanding their experiences of the world – and their interactions with others – which previously may have been confusing or misunderstood.

This is part of a broader shift towards viewing autism through a neurodiversity lens. Autism is seen by many not as a clinical condition, but as a natural variation in human thinking, communication and behaviour.

However, for other autistic people what they live with is more than difference – it is a profound disability that affects their capacity to live independently.

So, what are the downsides?

There is a worry from some parents, researchers and some autistic people themselves that increased focus on autistic people with milder presentations might have inadvertently impacted how we recognise and understand the needs of those with profound disability.

Visibility

Increasingly, autism is portrayed in traditional media – and particularly social media – through milder and more relatable experiences. This risks making those with more profound disability less visible in public consciousness.

Some parents have described their experiences of caring for autistic children with profound disability and the isolation they feel within a culture that increasingly views autism in a starkly different way to their lived reality.

Over-medicalisation

Broadening diagnostic boundaries also risks medicalising what are in fact broadly typical differences among developing children, meaning more children are viewed through a clinical lens.

Medicalisation can have unintended consequences. These include reducing expectations of the child and their development, and providing them therapeutic supports that may be unnecessary, inappropriate or harmful.

Resources

Historically, access to support in schools and disability systems such as the National Disabilty Insurance Scheme (NDIS) has been closely tied to whether someone has a diagnosis. As more people meet criteria for autism, it places more pressure on finite funding and clinical capacity.

When resources are stretched, it can be harder for those with the most complex needs to access the level of support they require for day-to-day life.

The government’s recently announced reforms for the NDIS recognise and respond to some of these tensions. Focus will shift towards providing funding support based on functional need, rather than diagnosis.

Research

With broader definitions, research has moved towards focusing almost exclusively on more cognitively able autistic individuals. While around 40% of autistic children have an intellectual disability, they make up only about 6% of research participants.

This means those who may stand to benefit the most from research that can improve quality of life are, often, the least represented in it.

Finding a balance between inclusion and precision

In many ways, the expansion of autism has been a story of progress. More people feel recognised. More individuals and their families have access to supports. And there is far greater community acceptance of difference.

But progress brings new challenges. As a concept for guiding research, evidence-based clinical practice and policy, the broadened definition of autism has been stretched to the point of breaking.

In response, some clinical and research experts have advocated for a separate diagnostic category of “profound autism” in order to better highlight the needs of these individuals. Others have warned this could undermine the social advances made, and force those with milder levels of disability back to the margins.

The challenge is to retain the gains of broader recognition while ensuring those with the most complex needs remain clearly in view. A spectrum can accommodate diversity. But it must have enough precision to guide action for those who need it the most.