Our autism spectrum disorder (ASD) articles are currently under expert review to take into account changes to the DSM (Diagnostic and Statistical Manual of Mental Disorders). Updated articles will be available in late 2013.
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.
What causes autism spectrum disorder (ASD)?
We don’t know exactly what causes ASD. But the latest research shows that in children with ASD:
- there’s early brain overgrowth (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 autism.
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.
ASD: difficulties and abilities
Children with 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 three main areas.
Social interaction and relationships
Children with ASD will appear to be uninterested in social contact with others. They:
- 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.
Communication and language
Children with ASD usually take longer than the average child to learn language. That means knowing fewer words, not using their words to communicate with others, or not speaking at all.
Children with ASD will find it hard to comprehend language, so understanding simple instructions and social norms can be difficult.
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.
Repetitive behaviour and routines
Even from a young age, children with ASD will often prefer the same routines: feeding, sleeping or leaving the house needs to be done the same way every time. They might be upset by changes like moving furniture or altering the usual familiar travel route.
Many children with ASD also like to repeat behaviour, sometimes in an obsessive way, like lining their toys up in a particular way over and over again. Younger children might like to collect things like twigs, string or balls. They’ll clutch tightly to their favourite objects and become upset if they’re removed.
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.
Any young child might show behaviours like the ones discussed above at different developmental stages. This isn’t necessarily a sign of autism. You know your child better than anyone – the key is to talk to someone if you have any concerns about your child’s development.
Different types of ASD
Autistic disorder (or autism)
Children with this diagnosis have difficulties with social relationships, verbal and nonverbal communication and repetitive behaviour. They might also have associated developmental delays – this means they haven’t reached certain milestones for their age. Read more on autistic disorder.
Children diagnosed with Asperger’s disorder generally don’t have developmental delays, and might have good language skills. They might have:
- unusual language patterns (such as speaking in a very formal way with a monotone voice)
- difficulties with social relationships
- narrow interests (so they can become easily fixated on a favourite topic).
Read more on Asperger’s disorder.
Pervasive Developmental Disorder – Not Otherwise Specified (PDD-NOS)
Children are diagnosed with PDD–NOS when they have some but not all the characteristics needed for a diagnosis of autistic disorder or Asperger’s disorder. Read more on PDD–NOS.
Diagnosis of ASD is based on a child not reaching certain age-based developmental milestones, because there are no other physical characteristics of the condition. The first sign of ASD that most parents notice is their child’s lack of interest in what’s going on around them. 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 accessing services and programs suited to your child’s needs.
A paediatrician, psychiatrist, psychologist or other trained professional in ASD can diagnose ASD. They’ll use a combination of behavioural tests (watching the child play and interact) and interviews with parents about the child’s development.
Read more about diagnosis.
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 ASD facts
The prevalence of 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 when diagnosing ASD.
Most studies focus on measuring the prevalence of ASD in general, or of autistic disorder. Fewer focus on Asperger’s disorder or PDD–NOS.