How is Autism Spectrum Disorder (ASD) Diagnosed?

When diagnosing Autism Spectrum Disorders, clinicians use a number of measures to determine whether or not an individual meets the criteria for a diagnosis. They may conduct observations, take a developmental history, and assess the individual’s communication skills, social and play skills, adaptive behaviour, and cognitive skills. Usually a number of professionals are involved in the diagnosis, including a paediatrician or psychiatrist, a psychologist, and a speech pathologist, and who come together to make a diagnosis based on their individual areas of expertise.

One of the items in a clinician’s tool kit is called the Diagnostic and Statistical Manual of Mental Disorders (or DSM for short). The DSM is a publication published by the American Psychiatric Association, and includes the diagnostic criteria for many different conditions, including those on the autism spectrum. In May 2013, the fifth edition of the DSM was published, and in it there have been some changes to the diagnostic criteria for ASD [1].


In May 2013 a new version of the Diagnostic and Statistical Manual of Mental Disorders (DSM) was launched – the DSM-5. The DSM-5 changes the way ASD is diagnosed. The changes reflect the current understanding of ASD, based on research.

New single diagnosis of ASD

This single diagnosis replaces the different subdivisions – autistic disorder, Asperger’s disorder and pervasive developmental disorder – not otherwise specified.

New severity ranking

An ASD diagnosis now has a severity ranking – level 1, 2 or 3. The ranking depends on how much support the person needs. This reflects the fact that some people have mild symptoms and others have more severe symptoms.

  • Level 1 – Requiring support
  • Level 2 – Requiring substantial support
  • Level 3 – Requiring very substantial support

ASD diagnosis based on two areas

Professionals will now diagnose ASD on the basis of difficulties in two areas. A child will need to have difficulties in both areas to be diagnosed with ASD. This approach replaces the previous three areas – social interaction, language and communication, and repetitive and restricted behaviour and interests.

Social and communication problems have been merged into one area – deficits in social communication. Difficulties in this area include rarely using language to communicate with other people, not speaking at all, not responding when spoken to, not responding appropriately to conversations, or not copying other people’s actions, such as clapping.

The second area is fixated interests and repetitive behaviour. Examples of this include lining toys up in a particular way over and over again, or having very narrow and intense interests.

Sensory sensitivities

Sensory sensitivities were not in the DSM-IV. In the DSM-5, they have been included as a behaviour within the fixated interests and repetitive behaviour category. Examples might be not liking labels on clothes, or eating only foods of certain colours or textures.

Symptoms from early childhood

According to the DSM-5, for a diagnosis of ASD a child must have had symptoms from early childhood, even if these are not recognised until later.

This change is to encourage professionals to diagnose ASD in early childhood. But it also means that a diagnosis can be made when it becomes clear that children’s abilities aren’t equal to the social demands being put on them. For example, at an age when a child is expected to have two-way conversations, you might notice that he can answer only simple questions.

Diagnosis of two or more disorders

If a child has other symptoms that meet the criteria for other disorders, she’ll be diagnosed as having two or more disorders – for example, ASD and ADHD.

New diagnosis of social communication disorder (SCD)

Social communication disorder (SCD) is similar to ASD. But according to the DSM-5, the main difference between SCD and ASD is repetitive behaviour. It will take time and clinical practice experience for the meaning of this category to become clear. If a child has at least two repetitive behaviours, it could point to a diagnosis of ASD. If not, it could point to a diagnosis of SCD.

Children who already have a diagnosis

If your child already has a diagnosis of autism spectrum disorder (ASD) – autistic disorder, high-functioning autism, Asperger’s syndrome or PDD-NOS – these changes won’t affect him. You don’t need to do anything and you can keep using these terms if you want to.

Some children who would have met the DSM-IV criteria for autism or related conditions might not meet the DSM-5 criteria. Some might be classified under the new category of social communication disorder (SCD).

A few children might miss out on a diagnosis. Recent research indicates that this is likely to be around 5% of children who meet the old criteria [2].

Rates of Diagnosis

The Centre for Disease Control and Prevention estimates that about 1 in 68 children has been identified with autism spectrum disorder That means that there are potentially 3450 persons with ASD within the NT [3].