For professionals: Autism spectrum disorder (ASD)

Access detailed information on autism spectrum disorder (ASD) screening, diagnosis, key publications and resources.

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What health professionals need to know about ASD

The definition of ASD is based on criteria from the Diagnostic and Statistical Manual of Mental Disorders. This manual, known as the DSM, serves as a basis for widely used assessment tools. It has wide-ranging influences on:

  • mental health research
  • diagnostic and treatment practices
  • social perceptions of mental illness

The DSM may influence diagnostic trends through changes to the criteria used to diagnose a specific disorder. The most recent release was the fifth edition (DSM-5) in May 2013. The DSM-5 defines ASD as a central diagnosis given to a continuum of complex conditions.

ASD as a single category

ASD is now a category that replaces previously diagnosed subtypes under the umbrella term of pervasive developmental disorders. This includes:

  • Rett syndrome
  • autistic disorder
  • Asperger’s disorder
  • childhood disintegrative disorder
  • pervasive developmental disorder (not otherwise specified)

The current classification system no longer mentions these subtypes or labels.

Symptoms previously attributed to these subtypes under the DSM-5 are now considered a representation of a continuum of symptoms. The severity levels (from mild to severe) of each subtype are categorized by levels of required support.

Specifiers for ASD

A person may present with additional symptoms that meet criteria for additional disorders. If so, the individual will be diagnosed as having 2 or more disorders. For example, a child could be diagnosed with both ASD and attention deficit hyperactivity disorder (ADHD). This is called a specifier.

The diagnosing clinician will state these results along with the ASD diagnosis. For example, they may indicate ASD with ADHD, or ASD with intellectual disability. This means that the individual met criteria for both conditions.

The new ASD diagnosis recognizes cases where symptoms show from early childhood, even if they are not recognized until later.

Screening for ASD in children

There is emerging research indicating that timely diagnosis and intervention can benefit children with ASD and other developmental disorders. Timely diagnosis is important as it is a necessary step in terms of identifying appropriate intervention(s).

When performing a preliminary assessment for ASD, a health professional or team of professionals will determine a child’s level of risk. They will use a combination of standardized questionnaires or tools and their clinical judgment.

Some more familiar screening tools in Canada include the:

  • Infant Toddler Checklist (ITC)
  • Social Communication Questionnaire (SCQ)
  • Autism Observation Scale for Infants (AOSI)
  • Autism Diagnostic Observation Schedule Toddler Module (ADOS-T)
  • Modified Checklist for Autism in Toddlers: Revised with Follow-Up (M-CHAT-R/F)

The first signs of ASD usually present in very early childhood. ASD can be detected through screening in children as young as 12 months old. However, parents are often the first to notice unusual development in their child.

Children with ASD demonstrate areas of concern that help to indicate when an assessment should be done. Not all signs are necessary for a child to receive a diagnosis of ASD.

Table 1: Symptoms of ASD and age when symptoms may be apparent.
Symptoms Age in months
6 to 8 9 to 11 12 to 14 15 to 17 18 to 21 21 to 24
General parental concern (for example, in motor or sensory development, or in sleep or play behaviour) X X X X X X
Shows weak head or neck control when being pulled into sitting position (namely, head lag) X          
Plays with toys in a restricted and/or unusual manner   X X X X X
Begins to develop language but then regresses in using it (for example, any loss of speech, babbling or social skills)   X X X X X
Engages in limited imaginative play   X X X X X
Displays repetitive or unusual movements involving fingers, hands, arms or head (namely, stereotypies)   X X X X X
Fixates on certain interests   X X X X X
Does not point and look (namely, coordination of eye gaze and action)     X X X X
Does not respond to name     X X X X
Displays unusual postures (for example, finger or hand flexing, tensing of arm, head tilting, mouth open or sticking out of tongue)     X X X X
Has trouble communicating       X X X
Demonstrates atypical motor behaviour or control         X X
Demonstrates behavioural issues, including self-injury         X X
Avoids eye contact         X X
Does not look to others for social clues when deciding on a reaction (namely, social referencing)         X X
Develops atypical use of language with respect to intonation or rhythm         X X
Demonstrates a stereotyped use of words or phrases (namely, echolalia where he or she repeats words or phrases without appearing to understand them)         X X
Is over- or under-responsive to environmental stimuli (namely, pain, heat, sounds, textures or lights)         X X

ASD develops differently in each individual. Unlike other conditions, there is no typical person with ASD. The term spectrum is used because symptoms can occur in combination or in degrees of intensity. Symptoms can also vary widely from relatively mild to debilitating.

Diagnosing ASD

An ASD diagnosis is based on a combination of factors and defines a severity level. This level is based on social communication and/or restricted, repetitive behaviour.

Similar to screening for ASD, health professionals specializing in diagnosing ASD may use any number of standardized tests. This is in combination with their clinical judgment.

Some more familiar diagnostic tools in Canada include the:

  • Childhood Autism Rating Scale (CARS)
  • Autism Diagnostic Interview – Revised (ADI-R)
  • Autism Diagnostic Observation Schedule (ADOS)
  • Developmental, Dimensional and Diagnostic Interview (3di)

The assessment may include a cognitive assessment to determine the person’s level of intellectual functioning, strengths and areas of difficulty.

The individual will most likely go through a series of simple procedures designed to allow the diagnostician to observe their behaviour. Other types of assessments may be conducted to better understand the unique physical, emotional, learning and behavioural needs of the individual.

Based on DSM-5 criteria, individuals with ASD are evaluated on 2 aspects:

  1. social communication and social interaction deficits
  2. restrictive or repetitive behaviours, interests or activities

The diagnosis is accompanied by a corresponding descriptor representing 1 of 3 levels of severity requiring support.

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