Exploring the List of Autism Spectrum Disorders

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Autism Spectrum Disorders

There is a broad list of autism spectrum disorders. The autism spectrum refers to a continuum of the degree of developmental impairment experienced by the individual, often a child, in question. autism spectrum disorders tend to have particular symptoms or characteristics in common, such as delayed and impaired communication, behavior, activity, social understanding, and interests. What divides these disorders and distinguishes them as unique is the severity of impairment, along with the particular types of symptoms, the onset age, and the degree to which the individual is challenged when engaging in social interaction. There are five autism spectrum disorders, which are classified as pervasive developmental disorders in the American Psychiatric Association’s Diagnostic and Statistical Manual and Mental Disorders, or DSM-IV.

Autistic Disorder

Autistic disorder, or AD, is the most common of the five autism spectrum disorders. It is also the most severe and affects roughly 20 out of 10,000 Canadians. Autism in itself can present with varying degrees of severity, as there are those with what is viewed as classic autism, who are relatively low-functioning, and those with high-functioning autism. Individuals with autistic disorder experience cognitive impairments and deficits in social understanding, verbal communication, and non-verbal communication. Autistic disorder also presents with restricted activities and unusual behaviors. Examples of these symptoms include avoiding eye contact, the inability to interpret facial and vocal cues, lack of empathy, and recurrent twirling or rocking. While these signs can be noticed as early as infancy in some cases, in others the child will seem to develop normally at first before symptoms of autism are detected.

Pervasive Developmental Disorder - Not Otherwise Specified

Pervasive developmental disorder mot otherwise specified, or PDD-NOS, is also called atypical autism. It affects slightly fewer individuals than autism disorder, at roughly 15 out of every 10,000 people. This autism spectrum disorder gleans its name from the fact that it does not meet the diagnostic criteria for autistic disorder, which is quite strict. Individuals with pervasive developmental disorder not otherwise specified experience impairment that is pervasive and severe in only some of the areas experienced by those with autistic disorder, such as social interaction or restricted interests and activities, but they will not meet both of these criteria at once.

Childhood Disinegrative Disorder

Childhood disinegrative disorder is another member of the autism spectrum disorders list. Often referred to as CDD, this is the rarest autism spectrum disorder, affecting 0.2 out of every 10,000 people. Children with this disorder appear to progress normally until around three years of age, or even older. After this age, they experience significant regression in areas such as cognitive ability, language, play, social behavior, and adaptive behavior.

Rett Syndrome

Rett syndrome is also a relatively rare autism spectrum disorder. It affects approximately 1 in 10,000 people, and it is almost exclusively females who are found with this developmental disorder. Like childhood disinegrative disorder, symptoms of Rett syndrome appear after the child seems to develop normally, but symptoms appear in children with Rett syndrome at around six to eighteen months' age. This disorder can present as a mild or severe case and is often misdiagnosed as cerebral palsy or autism. Rett sydrome presents with problems in emotional, sensory, motor, cognitive, and autonomic functions. This disorder can also impact movement, sensory perception, learning, communication, speech, and psychomotor skills, and it can have symptoms of physical distress as well, such as trouble with cardiac function, breathing, and movement.

Asperger Disorder

Asperger disorder, also referred to as AS and Asperger’s syndrome, impacts approximately 5 in 10,000 people, is often thought to be a mild form of autistic disorder. The affected individual experiences problems regarding communication and restrictive, repetitive interests and activities, while the impairments in social understanding and interaction can range from mild to severe. Unlike those with autistic disorder, individuals with Asperger disorder do not experience delays in cognitive development and language.


Autism Society Canada: Understanding Autism. Retrieved at https://autismsocietycanada.ca/understanding_autism/what_are_asds/index_e.html

National Institute of Neurological Disorders and Stroke: Autism. Retrieved at https://www.ninds.nih.gov/disorders/autism/detail_autism.htm#169863082