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What is Autism Spectrum Disorder?


by Dr Michael Smith

Autism spectrum disorder (ASD) is a developmental disorder that affects communication and behaviour. Although autism can be diagnosed at any age, it is said to be a “developmental disorder” because symptoms generally appear in the first two years of life.

According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), a guide created by the American Psychiatric Association used to diagnose mental disorders, people with ASD have:
  • Difficulty with communication and interaction with other people
  • Restricted interests and repetitive behaviours
  • Symptoms that hurt the person’s ability to function properly in school, work, and other areas of life
Autism is known as a “spectrum” disorder because there is wide variation in the type and severity of symptoms people experience. ASD occurs in all ethnic, racial, and economic groups. Although ASD can be a lifelong disorder, treatments and services can improve a person’s symptoms and ability to function. All caregivers should talk to their General Practitioner about ASD screening or evaluation in the first instance.

Signs and Symptoms of ASD

People with ASD have difficulty with social communication and interaction, restricted interests, and repetitive behaviours. The list below gives some examples of the types of behaviours that are seen in people diagnosed with ASD. Not all people with ASD will show all behaviours, but most will show several.

Social communication / interaction behaviours may include:
  • Making little or inconsistent eye contact
  • Tending not to look at, or appear to be listening to, people
  • Rarely sharing enjoyment of objects or activities by pointing or showing things to others
  • Failing to, or being slow to, respond to someone calling their name or to other verbal attempts to gain attention
  • Having difficulties with the back and forth of conversation
  • Often talking at length about a favourite subject without noticing that others are not interested or without giving others a chance to respond
  • Having facial expressions, movements, and gestures that do not match what is being said
  • Having an unusual tone of voice that may sound like sing-song, flat, or robot-like
  • Having trouble understanding another person’s point of view, or being unable to predict or understand other people’s actions or intent behind said actions
Restrictive / repetitive behaviours may include:
  • Repeating certain behaviours or having unusual behaviours. For example, repeating words or phrases, a behaviour called echolalia
  • Having a lasting intense interest in certain topics, such as numbers, details, or facts
  • Having overly focused interests, such as with moving objects or parts of objects
  • Getting upset by slight changes in a routine
  • Being more or less sensitive than other people to sensory input, such as light, noise, clothing, specific foods, or temperature

People with ASD may also experience sleep problems, and irritability. Although people with ASD experience many challenges, they may also have many strengths, including:
  • Being able to learn things in detail and remember information for long periods of time
  • Being strong visual and auditory learners
  • Excelling in math, science, music, or art

Causes and Risk Factors

While scientists don’t know the exact causes of ASD, research suggests that genes can act together with influences from the environment to affect development in ways that lead to ASD. Although scientists are still trying to understand why some people develop ASD and others don’t, some risk factors include:

Diagnosing ASD

Doctors diagnose ASD by looking at a person’s behaviour and development. ASD can usually be reliably diagnosed by the age of two. It is important for those with concerns to seek out assessment as soon as possible so that a diagnosis can be made, and treatment can begin.

Diagnosis in children and adolescents

ASD symptoms in children and adolescents who attend school are often first recognized by parents and teachers, and then may be referred to the Special Education Service of the Ministry of Education. The Special Education Service can also be contacted directly on 0800 622 222 or email

A specialist may perform an initial evaluation and then recommend these children visit their primary health care doctor initially, or be referred to a paediatrician who specialises in ASD for additional testing, if a formal diagnosis is sought. A formal diagnosis is required in order to access a variety of funding options, and to apply for in-school support.

Parents may talk with these specialists about their child’s social difficulties including problems with subtle communication. These subtle communication issues may include problems understanding tone of voice, facial expressions, or body language. Older children and adolescents may also have trouble understanding figures of speech, humour, or sarcasm. Parents may notice that their child has trouble forming lasting friendships.

Diagnosis in adults

Diagnosing ASD in adults is often more difficult than diagnosing ASD in children. In adults, some ASD symptoms can overlap with symptoms of other mental-health disorders, such as anxiety or attention-deficit/hyperactivity disorder (ADHD).

Adults who notice the signs and symptoms of ASD should talk with a doctor and ask for a referral for an ASD evaluation. While testing for ASD in adults is still being refined, adults can be referred to an Adult Mental Health Service in the first instance. A clinician will ask about concerns, such as:
  • Social interaction and communication challenges
  • Sensory issues
  • Repetitive behaviours
  • Restricted interests
Information about the adult’s developmental history will help in making an accurate diagnosis, so an ASD evaluation may include talking with parents or other family members.

Getting a correct diagnosis of ASD as an adult can help a person understand past difficulties, identify his or her strengths, and obtain the right kind of help. Studies are now underway to determine the types of services and supports that are most helpful for improving the functioning and community integration of transition-age youth and adults with ASD.



The role of The National Institute of Mental Health (NIMH) is gratefully acknowledged in the compilation of this document.
Article posted 18 January 2019
Michael Smith psychologist auckland autism
Dr Michael Smith is a Registered Psychologist with a private practice in Auckland.
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