This chapter provides an overview of autism spectrum disorder, the diagnostic process, the prevalence of autism in Australia, and the diversity of the autism spectrum.
What is autism spectrum disorder?
Autism spectrum disorder (autism) is a lifelong neurodevelopmental condition that affects how people communicate, interact, and make sense of the world. Autistic people experience difficulties with communication and social interaction, sensitivity to sensory inputs, and restricted or repetitive interests and behaviours (see Box 2.1). In some cases, the difficulties experienced by autistic people may also lead to behavioural challenges.
There is no known cause of autism. Current evidence suggests that autism results from changes to the development and growth of the brain, which may be caused by a combination of genetic, developmental and environmental factors. Genetic factors appear to be particularly significant. For example, family members of an autistic person tend to have higher rates of autistic traits, the concordance rate of autism in twins is higher in identical twins than in fraternal twins, and families with one autistic child are more likely to have another autistic child when compared to the general population.
Despite the myths that surround the condition, autism is not the result of bad parenting or vaccination. Neither is it a childhood condition, one that affects boys only, or something that can be 'cured'.
While behavioural characteristics of autism are often present very early in life—in some cases from birth—they may not become obvious to other people until the school years, or sometimes even later.
Box 2.1: Characteristics of autism spectrum disorder
Difficulties with social-emotional reciprocity
For example, being unable to maintain normal 'back and forth' conversations, having little or no interest in sharing interests and emotions, or displaying little or no interest in social interactions.
Difficulties with non-verbal communication
For example, abnormal eye contact, difficulties understanding and using gestures, body language and facial expressions.
Difficulties developing and maintaining relationships appropriate to age and development
For example, a child may have difficulties with imaginative play and making friends.
Stereotyped or repetitive speech, movements, or use of objects
For example, lining up toys, flapping hands, toe walking, or echolalia (repeating words and phrases).
Inflexible adherence to routines, patterns or behaviour, and becoming distressed at changes
For example, eating the same foods, travelling the same route to a location.
Sensory hyper- or hypo-reactivity
For example, to sounds, textures, smells, touch or pain.
Restricted or fixated interests
For example, only playing with certain toys, or discussing certain topics.
How is autism diagnosed?
There is no definitive test for autism. Diagnosis is made on the basis of developmental assessments and behavioural observations.
Since 2013, autism has been diagnosed using the American Psychiatric Association's Diagnostic and statistical manual of mental disorders (5th edition)—commonly referred to as the DSM-5. The DSM-5 introduced a single diagnosis of 'autism spectrum disorder'. This replaced the former sub-categories of 'autistic disorder', 'Asperger syndrome', 'childhood disintegrative disorder' and 'pervasive developmental disorder – not otherwise specified'.
The DSM-5 defines how many autistic characteristics must be present in order to confirm a diagnosis of autism. To be diagnosed, a person must have difficulties with 'social communication' and 'restricted, repetitive and/or sensory behaviours or interests'. Signs must also have been present from early childhood, even if they were not recognised at the time. (see Appendix 3.A)
The DSM-5 also requires assessors to specify the severity of symptoms as Level 1, 2 or 3. Each level relates to the amount of support needed for daily function. Examples of symptom severity at each level include:
Level 1 – requires support
social communication deficits cause noticeable impairments, difficulty initiating social interactions and clear examples of atypical or unsuccessful responses to social overtures, possible decreased interest in social interactions; and
inflexible behaviour interferes with functioning in one of more contexts, difficulty switching between activities, organisation and planning problems hamper independence.
Level 2 – requires substantial support
marked deficits in verbal and non-verbal social communication skills and evident social impairment (even with support in place), reduced or abnormal responses to social overtures; and
inflexible behaviour, difficulty coping with change, or other restricted/repetitive behaviours are noticeable to casual observers and interfere with functioning in a variety of contexts, distress and/or difficulty changing focus or action.
Level 3 – requires very substantial support
severe deficits in verbal and non-verbal social communication cause severe impairments in functioning, very limited initiation of social interactions and minimal response to social overtures; and
inflexible behaviour, extreme difficulty coping with change, or other restricted/repetitive behaviours interfere markedly with functioning in all spheres, great distress/difficulty changing focus or action.
Prevalence of autism in Australia
Stakeholders spoke of a lack of accurate, comprehensive data on the prevalence of autism in Australia. This was attributed in part to problems with data collection, including the lack of a register to monitor autism diagnoses, as well as general challenges in determining the true prevalence of autism given increasing awareness of autism, improved diagnosis of autism, and changes in diagnostic criteria.
The most recent figures from Australian Bureau of Statistics (ABS) show that in 2018 there were 205 200 autistic individuals in Australia—a 25.1 per cent increase since 2015. However, a number of submitters questioned the accuracy of the figures, with most suggesting they underestimated the true prevalence of autism in Australia. As an example, one submission cited a study that put the actual prevalence of autism in Australia at between 2.4 and 4.4 per cent of the population, or between 600 000 and 1 million people.
The most commonly cited alternative to the ABS figures was a prevalence rate of 1 in 70 people, calculated in 2018 by Autism Spectrum Australia using prevalence data in comparable countries, such as the United States of America and Canada, as well as local Australian data. Based on the current Australian population, this would equate to approximately 367 200 Australians who would meet the diagnostic criteria for autism, meaning it is likely the ABS figures underestimate the prevalence of autism in Australia by over 160 000.
Prevalence by age
ABS data indicates much higher prevalence rates of autism among children and early teens compared to any other age group (see Figure 2.1).
Figure 2.1: Prevalence of autism by age – 2015 and 2018
Source: Australian Bureau of Statistics, Disability, Ageing and Carers, Australia: Summary of Findings 2018.
The most commonly cited reasons for the drop in prevalence were changes to the diagnostic criteria over time, inadequate record keeping and a lack of research, as well as the under-diagnosis of autistic adults. The under‑diagnosis of adults was thought to be primarily a function of the cost of diagnosis. Other suggested barriers to diagnosis included a lack of information about autism and fears about the impact of a diagnosis, including experiencing stigma and discrimination.
The ABS also theorised that another factor in the decline may be the way its survey was conducted, with a surveyor speaking to the first available adult in a household to determine if there was an autistic person living there. The ABS suggested that while parents may be willing to reveal their children's diagnoses, those children may be less likely to reveal they are autistic once they have moved out of home.
Other theories about the drop in prevalence included people 'losing' their diagnosis over time—although it was noted that the reasons for this needed to be explored further, with Monash University stating that such research would need to include 'whether treatment has been effective or whether children have been unnecessarily diagnosed with autism'.
Prevalence by gender
The ABS data from 2018 indicated that males were 3.5 times more likely than females to be diagnosed with autism. While this gap had narrowed since 2015, when males were 4.1 times more likely to be diagnosed with autism, a number of stakeholders argued the figures may still not reflect the true male to female ratio of autism and that females are still underrepresented in the statistics.
The most commonly cited reasons for higher prevalence in males were that autistic females may present differently to males and are better able to mask social differences, and that there is a gender bias in current diagnostic tools.
Clinical knowledge was also thought to contribute to the gender gap by delaying diagnosis of females with autism, as well as under diagnosing females with co-occurring intellectual disability.
Gender diversity and sexual orientation
It was also noted that the female presentation of autism may also be present in atypical and gender diverse males who can experience challenges in diagnosis.
There is growing evidence of an increased prevalence of gender variance in autistic people compared to the general population. Additionally, autistic people are also more likely than the general population to experience gender incongruence.
Non-heterosexual orientation is also more common among autistic people than in the general population, with greater variability in sexual orientation among females.
Prevalence in specific cohorts
Given the lack of general data on the prevalence of autism in Australia, the data on prevalence in specific cohorts, such as Aboriginal and Torres Strait Islander peoples and those from culturally and linguistically diverse (CALD) backgrounds, is also deficient.
Aboriginal and Torres Strait Islander peoples
Little is known about the prevalence of autism in Aboriginal and Torres Strait Islander peoples. However, given the high prevalence of disability in Indigenous Australians, stakeholders suggested that the autism is likely to be undiagnosed in Aboriginal and Torres Strait Islander peoples for a number of reasons, including:
barriers to accessing diagnostic services;
misdiagnosis with schizophrenia or Foetal Alcohol Spectrum Disorder;
hearing loss and otitis media (which can delay or mask an autism diagnosis);
shame and stigmatisation around disability; and
cultural and language barriers.
Culturally and linguistically diverse communities
As with prevalence in Aboriginal and Torres Strait Islander peoples, there is an absence of data on the prevalence of autism in people from CALD backgrounds in Australia. It was suggested that autism may be under-diagnosed in CALD individuals due to a lack of knowledge about autism, language barriers, and/or cultural traits—such as very fixed social rules or different expectations about looking people in the eye—that may mask symptoms.
Diversity of the autism spectrum
When describing the diversity of autistic people, numerous stakeholders referenced the well-known quote by Dr Stephen Shore—'if you've met one person with autism, you've met one person with autism'.
This reflects the nature of autism as a 'spectrum' condition. The term spectrum is used to emphasise that autism presents differently in each individual and may also change over time. As explained by the Cooperative Research Centre for Living with Autism (Autism CRC):
Every person on the autism spectrum is unique. The developmental challenges and their presentation can vary widely in the nature and severity between individuals, and in the same individuals over time.
Some stakeholders also stressed that the spectrum is not a linear scale of autism severity. Rather, it is better described as a 'constellation' of traits (Figure 2.2). As one witness explained:
…it's a spectrum. But at the moment people are looking at it as a linear line, like 'he's low functioning, he's high functioning'. Autism isn't a linear spectrum. Autism is a colour palette spectrum. It's a soundboard spectrum, where every single person on the spectrum fits into a different part.
Figure 2.2: Autism spectrum traits
Source: Amaze, Talking about autism: guidelines for respectful and accurate reporting on autism and autistic people, p. 5.
The diversity of autism presentation is also impacted by the high number of co‑occurring physical and psychiatric conditions experienced by autistic people. According to the Raising Children website, nearly 75 per cent of autistic children have a co-occurring condition. Chief Clinical Adviser and Founder of ND Australia, Professor Adam Guastella, explained to the committee that it was not surprising that comorbidities were high across neurodevelopmental disorders:
…a child who starts to show difficulties or divergence in one domain of functioning, whether it's social, motor language or cognitive development, will start to show delays or divergence in other areas of development.
Commonly co-occurring conditions include intellectual disability and developmental delays, language delay, motor difficulties, epilepsy, sleep problems, anxiety, depression, attention deficit hyperactivity disorder (ADHD), unusual eating behaviours, and gastrointestinal symptoms. ND Australia provided the following estimation of the rate of certain comorbidities:
30–40 per cent of autistic children have an intellectual disability or developmental delays;
60–70 per cent of autistic people have ADHD;
40–60 per cent of autistic children have anxiety;
20–30 per cent of autistic people have epilepsy;
4–5 per cent of autistic children have Tourette syndrome and another 9–12 per cent have tics of some kind;
30 per cent of children with Cerebral Palsy are also autistic; and
up to 40 per cent of people with Down Syndrome are also autistic.
These co-diagnoses 'profoundly affect' how a person with autism functions.
Variation and complexity of needs
Autism has been described as 'among the most complex, prevalent and heritable of all neurodevelopmental conditions'. Its complexity is reflected in the broad diagnostic 'umbrella' of Autism Spectrum Disorder, which a submitter noted 'covers people in very different "worlds", with vastly diverse experiences and conflicting worldviews regarding autism'.
Accordingly, there is significant variation in the presentation of autism and the complexity of autistic people's support needs. For example, while some autistic people are able to live completely independently, most experience difficulties negotiating everyday living and a 'significant proportion' have multiple and complex needs that necessitate intensive intervention and long‑term support. As described by the Royal Australasian College of Physicians:
A child at one end of the spectrum may only need minimal supports to reach their potential while another child, with the same condition, may have complex problems that require lifelong care.
This variation was also reflected in personal experiences conveyed to the committee by stakeholders in the inquiry, with some having achieved personal and professional success with minimal or no government support, while others struggled to manage the routine activities of daily living.
The committee notes that the breadth of the spectrum appears to be the source of some tension in the autism community, particularly between autistic adult self-advocates and parents of autistic children with more 'severe' autism and cognitive and functional impairments. More than one participant suggested that alternative classifications or sub-classifications may be needed to help improve understanding of the differences and challenges across the autism spectrum.
Within the autism spectrum, those diagnosed as Level 2 or Level 3, and/or those with significant co-occurring conditions, are likely to have more substantial and complex support needs. Individuals with more complex needs may be non-verbal and experience significant behavioural issues and anxieties. They are also likely to need assistance with self-care activities, such as showering, dressing, toileting and food preparation. They may also require full‑time supervision.
While the committee heard there is no clear definition of 'complex needs' (particularly in relation to the National Disability Insurance Scheme [NDIS]), stakeholders indicated that those with complex needs can include individuals presenting with more 'severe' autism, intellectual disability, mental health conditions, behaviours of concern and language disorders.
However, others noted that complex needs can also arise from the intersection of autism with 'contextual stressors', such as poverty, unaccommodating environments, drug and alcohol dependence, unsafe home environments, and/or contact with the criminal justice system. Late diagnosis can also lead to autistic people presenting with 'preventable conditions that can be severe and complex in nature'.