By Raising Children Network
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Girl with ASD with parents behind credit iStockphoto/Juanmonino

did you knowQuestion mark symbol

  • In 2009 in Australia, over 42 000 children aged 0-14 years had been diagnosed with ASD.
  • In 2007, the UN nominated 2 April as World Autism Awareness Day. The day was first observed in 2008.
Autism spectrum disorder (ASD) is a group of conditions that cause people to have difficulties with social communication, to have narrow interests and repetitive behaviours, or to be over-sensitive or under-sensitive to taste, touch, sight or sounds.

About autism spectrum disorder

Autism spectrum disorder (ASD) is a brain-based condition – that is, where the brain hasn’t developed in a typical way. Although no two children with ASD are the same, they all face challenges in interacting and communicating with others. And they also have either a narrow range of interests or engage in repetitive activities.

What causes autism spectrum disorder?

We don’t know exactly what causes autism spectrum disorder (ASD). But the latest research shows that in children with ASD:

  • there’s early brain overgrowth, which means the brain grows faster than average
  • different parts of the brain don’t communicate with each other in a typical way.

Evidence also strongly suggests a genetic basis to ASD – that is, the condition might come from the complex interaction of several genes involved in brain development.

Read more about what causes ASD.

There’s no one answer to the question of what causes ASD. It is clear, however, that what parents do or don’t do doesn’t cause ASD in their child.

Autism spectrum disorder: difficulties and abilities

Children with autism spectrum disorder (ASD) have a wide range of difficulties and abilities. In fact, some have very impressive skills and strengths. One child with ASD might know lots of words and have a very good memory. Other children might respond mostly to things they can see, making them good at completing puzzles and sorting objects by shape and colour.

By about the age of three, however, all children with ASD will show difficulties in two main areas – social communication, and interests and behaviour.

Social communication
Children with ASD usually take longer than other children to learn language and often find it hard to make sense of language, so understanding simple instructions and social norms can be difficult. Almost all children with ASD learn at least some language but they don’t always communicate for purely social reasons and often appear to be uninterested in social contact with others.


  • might not respond when people speak or gesture towards them, even when their names are called out
  • often make little eye contact with others and usually won’t copy other people’s actions, like clapping or waving
  • usually don’t share interests with others, rarely pointing at anything or showing interest in giving or sharing
  • aren’t very interested in chatting or playing, especially with other children.

When children with ASD do have language skills, they:

  • will talk about their own special interests, and rarely use language skills to communicate with others
  • might focus on categorising everything around them, such as labelling all their toy trains
  • might echo what they hear, repeating patterns of words without attaching any meaning to them
  • rarely use nonverbal gestures, like nodding their heads or hand gestures, to communicate.

Narrow interests and repetitive behaviour
Even from a young age, children with ASD will often prefer the same routines. They might:

  • need to eat from the same plate and drink from the same cup at every meal
  • take the same route from home to child care each time
  • be upset by changes like moving furniture. 

Many children with ASD also like to repeat behaviour, sometimes in an obsessive way. They might:

  • like to repeatedly flick switches or open and shut doors
  • like lining their toys up in a particular way over and over again
  • like to collect things like twigs, string or balls
  • tightly clutch their favourite objects and become upset if they’re taken away.

Older children with ASD might have very narrow and intense interests. For example, they might be interested in trains, always choosing a toy train over other toys, labelling every train in their surroundings, and insisting on repeatedly watching cartoons or videos that feature trains. If they have strong verbal skills, they might talk only about trains.

Sensory sensitivities
Many children with ASD also have sensory issues. They might:

  • be especially sensitive to sound and raise their hands to their ears to block out noise
  • like to watch spinning objects, such as fans and wheels
  • like the feel of objects with a certain texture
  • want to eat only foods with a certain texture – for example, they might be happy to eat soft, smooth food, but will refuse anything lumpy
  • use their peripheral vision a lot, or tilt their heads to look at objects from a particular angle.
Any young child might behave in the ways listed above at different developmental stages. This isn’t necessarily a sign of autism spectrum disorder (ASD). You know your child better than anyone – the key is to talk to a child health professional if you have any concerns about your child’s development.

Different types of autism spectrum disorder

In May 2013 the criteria that health professionals use to diagnose autism spectrum disorder (ASD) was changed. Before then, there were different types of ASD – autistic disorder, Asperger’s disorder (also called Asperger’s syndrome), and pervasive developmental disorder – not otherwise specified (PDD–NOS).

Under the diagnostic manual (DSM-5), there is just ASD.

Video Early signs of autism spectrum disorder

In this short video, parents talk about noticing the early signs of autism spectrum disorder (ASD) in their children, including differences in typical developmental behaviour and milestones. They say that it helps to understand developmental milestones so you can act if you’re worried or you think something is wrong. The earlier you act, the better off your child will be.

Autism spectrum disorder diagnosis

Diagnosis of autism spectrum disorder (ASD) is based on a child not reaching certain age-based developmental milestones, because there are no other physical characteristics of the condition.

Signs of ASD are often present early in infancy, but become more noticeable in the toddler years, as children are expected to start talking and playing with other children. The first sign of ASD that most parents notice is their child’s lack of interest in other people. For example, many babies later diagnosed with ASD don’t look at their parents while being held or during nappy changes.

Children who are diagnosed with ASD will get a description of how severe their symptoms are and the amount of support they need. This ranges from `requiring support’ to ‘requiring very substantial support’.

Health professionals will also look at children’s language and cognitive abilities. Some children with ASD have intelligence in the typical range, but others have below-average intelligence.

Children who show difficulties in social communication only might be diagnosed with social communication disorder, rather than ASD.

If you’re concerned about your child’s development, talk to your health care provider about a developmental assessment. Finding out for sure is the first step to helping your child and getting services and programs suited to your child’s needs.

It’s important to get help and support as soon as possible. The sooner children get early intervention services, the more effective these services can be.

A paediatrician, psychiatrist, psychologist or other professional trained in ASD can diagnose ASD. They’ll use a combination of behaviour tests (watching the child play and interact) and interviews with parents about the child’s development.

Read more about ASD diagnosis.

Video Getting the diagnosis – what and how

This short video features parent stories about children's autism spectrum disorder (ASD) diagnoses. Parents share their experiences of the process, from spotting first warning signs to getting a diagnosis. They note that getting a diagnosis is not always quick or easy, but it's important to persevere.

I wish I’d known that autism looks different in every child. A friend’s little boy was diagnosed with autism but he was very different from my son – her boy had no language and lost all eye contact with others. Although I knew something was wrong with my son, I didn’t think it was autism because not only did he have some words, he would look at me and smile.
– Jenny, mother of Alexander, aged five

Other autism spectrum disorder facts

The prevalence of autism spectrum disorder (ASD) has risen since the 1990s. Research suggests that the apparent increase is at least partly because of:

  • increased awareness about ASD, so more cases are being identified
  • changes in the criteria for diagnosing ASD.

Some researchers suggest that recent changes in the criteria used when diagnosing ASD will affect the number of people diagnosed with ASD. Some argue that the changes will lead to an increase in the number of people diagnosed with ASD, while others think it will lead to a decrease. This is because of the diagnostic criteria and how researchers measure prevalence.

In the past, most studies focused on measuring the prevalence of ASD in general, or of autistic disorder. Fewer focused on Asperger’s disorder or PDD–NOS. Now that all these categories have been combined into one, it’s likely to affect the prevalence of ASD.

  • Last updated or reviewed 07-10-2015
  • Acknowledgements This article was developed in collaboration with Cheryl Dissanayake and Cherie Green, Olga Tennison Autism Research Centre, La Trobe University.