Autism: For professionals

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• Autism spectrum disorder
• Diagnosing autism spectrum disorder

Autism spectrum disorder

The diagnosis of autism spectrum disorder (also known as autism or ASD) is based on criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM). This manual is the basis for widely used assessment tools. It influences:

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

The DSM can also influence diagnostic trends by changing the criteria for specific disorders. The most recent release was the fifth edition (DSM-5) in May 2013. A revised version of the fifth edition (DSM-5-TR) was released in March 2022 . The DSM-5 defines autism spectrum disorder as a central diagnosis given to a continuum of complex conditions.

Autism as a single category

Autism spectrum disorder now includes subtypes that used to be diagnosed under the umbrella term of pervasive developmental disorders. This includes:

• 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.

Signs and symptoms previously attributed to these subtypes under the DSM-5 are now considered part of a continuum of Autistic traits and characteristics. The severity levels (from mild to severe) of each subtype differ by levels of required support.

Screening for autism in children

A timely diagnosis and intervention can benefit children on the autism spectrum and with other developmental disorders. Timely diagnosis is a necessary first step for identifying and beginning appropriate therapies and supports.

When assessing a child for autism spectrum disorder, a health professional or team of professionals will determine a child's level of risk. They will use standardized questionnaires or tools as well as 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 autism spectrum disorder are usually present in very early childhood. Parents are often the first to note concerns about their child's development. Autism can be detected through screening in children as young as 12 months old.

Children on the autism spectrum may show signs across many areas of development. Not all signs are necessary for a child to receive a diagnosis of autism spectrum disorder.

Autism develops differently for each person. The term spectrum is used because symptoms can occur in combination or in degrees of intensity. Symptoms can also vary widely from person to person and across the lifespan.

Early signs and symptoms for autism spectrum disorder

Age in months	Clinical presentation
6 to 12	Limited smiles or other joyful expressions directed at people Limited or no eye contact Limited reciprocal sharing of sounds, smiles, or facial expressions Diminished, atypical, or no babbling or gesturing (e.g., pointing, reaching, waving 'bye-bye') Limited response to name
9 to 12	Emerging repetitive behaviours (e.g., spinning or lining up objects) Unusual play (e.g., intense visual or tactile exploration of toys)
12 to 18	No single words Absence of compensatory gestures (such as pointing) Lack of pretend play Limited joint attention (initiating, responding, sharing of interests)
15 to 24	Diminished, atypical, or no spontaneous or meaningful two-word phrases
Any age	Parental and other caregiver concerns about the possibility of autism
Any age	Developmental regression (loss of skills): reduced frequency or loss of social behaviours (e.g., directing eye gaze to others) and communication (words and gestures) relative to earlier age

Adapted from: Canadian Pediatric Society

Diagnosing autism

An autism spectrum disorder diagnosis is based on a combination of factors and specifies the level of support that a person may need.

Similar to screening for autism spectrum disorder, diagnostic specialists may use any number of standardized tests. This is in combination with their clinical judgment.

Some 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)

A cognitive assessment can help determine the person's:

• strengths
• areas of difficulty
• level of intellectual functioning

The person will most likely be asked to participate in or complete a series of tasks which will allow the diagnostician to observe their behaviour. Other types of assessments may be conducted to better understand their unique physical, emotional, learning and behavioural needs.

Based on DSM-5 criteria, individuals on the autism spectrum are evaluated on 2 main aspects of development:

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

The diagnosis is accompanied by documentation that details:

• a definitive diagnosis of autism spectrum disorder
• any co-occurring conditions that may have been observed or screened for
• information to help identify the level of support needed

Related links

• Canadian Paediatric Society: Autism Spectrum Disorder
• Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R/F)