Information on Autism Spectrum Disorder

Information on Autism Spectrum Disorder

Defining Autism Spectrum Disorder (ASD)

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is characterized by:

1) Persistent deficits in social communication and social interaction across multiple contexts. Individuals will have difficulty:

  • Developing, maintaining and understanding relationships with others;
  • Understanding non-verbal communication, such as gestures, facial expression and body language;
  • Communicating with others and sharing common interests.

2) Restricted, repetitive patterns of behaviour, interests, or activities. Individuals with ASD have:

  • Repetitive motor movements, object use, or speech;
  • Difficultly changing their routines as consistency and rituals with routines need to remain the same;
  • A fixation with unusal objects or interests;
  • A hyper- or hyposensitive sensory system when interacting with their environment.

For your child to be diagnosed with ASD, the symptoms must be present in the early developmental period (typically recognized in the first two years of life). Symptoms of ASD tend to cause impairments in social, occupational, or functional areas of daily life. Individuals with ASD may experience different levels of impairment at different times of their life, depending upon their stage of development, outside stressors, and social demands of their situation.

It is important to note that based on the changes made in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), ASD now encompasses disorders previously referred to as: early infantile autism, childhood autism, Kanner’s autism, high-functioning autism, atypical autism, pervasive developmental disorder not otherwise specified, childhood disintegrative disorder, and Asperger Syndrome.

Behaviours of ASD

To learn more about the common behaviours seen in individuals with ASD,  visit the “Behaviours” page.

Levels of Impairment

The latest edition of the DSM-5 no longer includes types of disorders. The term “spectrum” refers to the wide range of symptoms, skills, and levels of impairment or disability that children with ASD can have. Some children are mildly impaired by their symptoms, while others are severely disabled. The health care professional that is assessing and diagnosing your child will rate their impairment in two areas: social communication and restricted, repetitive behaviours. Individuals are given an impairment rating based on the symptoms and skills they exhibit. The impairment scale is rated as:

  • Level 1: Individual requires support
  • Level 2: Individual requires substantial support
  • Level 3: Individual requires very substantial support

Facts About ASD

Here are some important facts that you should know about ASD:

  • ASD is commonly diagnosed in early childhood between 2 and 3 years of age. However, ASD can be diagnosed as early as 12 months of age if signs and symptoms are more severe, or in later years if signs and symptoms are not as noticeable. Go to the “Assessment and Diagnosis” page to learn more.
  • ASD is four times more likely to be diagnosed in males than in females.
  • The DSM-5 reports that about 1% of the population in both U.S. and non-U.S. countries have ASD.
  • There is no exact cause of ASD. There is research done that shows that both genetic and environmental factors can cause an individual to have ASD.
  • Many individuals with ASD will have co-morbid disorders, such as an intellectual impairment and/or mental health illnesses.  Visit our “Co-Morbid Disorders” page to learn more.
  • Currently there is no cure for ASD. However, there are multiple therapies and intervention strategies that have been shown to be effective for individuals who have ASD.  Visit the “Therapy Options” page to learn more.

Understanding the Terminology of ASD

The terminology of autism can be very confusing and overwhelming. Some individuals who have ASD refer to themselves as having ASD, autism, Asperger Syndrome, and pervasive developmental disorder (PDD). You may also hear people refer to ASD as autistic disorder, childhood autism, or infantile autism. This is largely due to the recent changes the DSM-5 made to their diagnostic criteria.

It is also important to note that although the previous type of autism labeled PDD and the new term autism spectrum disorder largely or entirely overlap, PDD was intended to describe a specific set of diagnostic features. Now, ASD links various signs, symptoms and features which is why the term ‘spectrum’ is added to the title. ASD is now used as an umbrella term to describe the autism behaviours that are seen in a wide range of individuals.

ASD Before the Diagnostic and Statistical Manual of Mental Disorders Version 5 (DSM-5)

A revision to the diagnosis and terminology associated with autism spectrum disorder (ASD) was proposed in the Diagnostic and Statistical Manual of Mental Disorders version 5 (DSM-5), released in May 2013. The new diagnosis of ASD encompasses previous autism disorder types, such as Asperger syndrome, childhood disintegrative disorder, and PDD-NOS and Rett Syndrome. You may still hear people who have ASD or families members refer to these types of autism disorders as these disorders remain an important part of their identity. It may be helpful to understand how these disorders were historically classified and learn about the key aspects setting each apart from the others.

Asperger Syndrome

Asperger Syndrome (AS), also known as Asperger Disorder (AD) or simply Asperger’s, was a type of autism disorder that was characterized by significant difficulties in social interaction and nonverbal communication, alongside restricted and repetitive patterns of behavior and interests. It differed from other autism disorders because individuals were able to develop and maintain good language and intellectual functioning. Physical clumsiness and odd uses of language were also frequently hallmarks of AS.

The modern conception of Asperger Syndrome came into existence in 1981 and became standardized as a diagnosis in the early 1990s. The diagnosis of Asperger’s was eliminated in the 2013 fifth edition of the DSM-5 and replaced by a diagnosis of autism spectrum disorder on a severity scale.

To learn more about Asperger Syndrome please visit:

Asperger Manitoba Inc. website:

Childhood Disintegrative Disorder

Childhood Disintegrative Disorder, also known as Heller syndrome, was characterized by a loss of previously learned language and social skills, resulting in a persistent delay in these areas. Social and emotional development also disintegrate, resulting in an impaired ability to relate with others.

Childhood disintegrative disorder was a specific type of autism disorder because an individual with this disorder showed severe regression after several years of normal development and had a more dramatic loss of skills than a child with more “classic” autism did.

Pervasive Development Disorder – Not Otherwise Specified (PDD-NOS)

PDD-NOS comprises a series of signs and symptoms of both autism and developmental delays (or pervasive development disorder). In essence, it’s a diagnosis that means “on the autism spectrum, but not falling within any of the existing specific categories of autism.”

Many children diagnosed with PDD-NOS had some symptoms of PDD and some symptoms of another type of autism disorder, but not enough of any one to receive a diagnosis. Thus, they did have a PDD — but they did not have one of the other types of autism disorders, such as Rett syndrome, childhood disintegrative disorder, Asperger syndrome, or autism. As a result, they received the catch-all diagnosis of PDD-NOS.

The common belief was that the diagnosis PDD-NOS meant that a child has a touch of autism. A child may have had only a few mild symptoms of a PDD and still qualified for the PDD-NOS label. On the other hand, the child may have had very severe delays in language and communication skills, but still not qualified for a specific autism diagnosis.

To learn more about PDD-NOS, please visit:
Autism Speaks – PDD-NOS website:

Rett Syndrome

Rett syndrome was a previous type of autism almost exclusively affecting girls. It is characterized by normal early growth and development followed by a slowing of development.

The course of Rett syndrome, including the age of onset and the severity of symptoms, varies from child to child. As the syndrome progresses, the child loses purposeful use of the hands and the ability to speak. The loss of functional use of the hands is followed by compulsive hand movements, such as wringing and hand washing. Other signs and symptoms may include problems in crawling or walking, slowed brain and head growth, seizures, and intellectual disability.

In the DSM-5 Rett Syndrome is no longer a type of autism, but is now a differential diagnosis to autism spectrum disorder.

For more information on Rett Syndrome, please visit: website: