Those living in the world of autism, whether through a family member, a student, a friend, or being personally affected, are very familiar with the term “autism spectrum disorder.” Just what does “spectrum” mean, and what is involved in being “on the spectrum”? The spectrum has been pictured as an umbrella, a flow-chart, and a Venn diagram. However, since so many spectrum disorders overlap, it is appropriate to picture the spectrum as a continuum of disorders that are based on how they “look” and how complex they are.

Picturing the Autism Spectrum

Imagine a long angle lying on its side with the pointed vertex to the left and the rays, or sides of the angle, opening to the right. The name of this angle is Pervasive Developmental Disorders (PDDs), which is the overall classification for autistic disorders in the DSM-IV. Pervasive Developmental Disorder is a generic term referring to a group of disorders that are characterized by impairments in social interaction, verbal and nonverbal communication as well as patterns of behaviors such as rocking, hand flapping, toe walking, and hair pulling. Symptoms may vary significantly among individuals with PDD, not only in form but in how severe they are. The vertex (point) of the angle represents the conditions that are easier to diagnose. As the angle becomes wider, diagnosis becomes more difficult due to variation and presentation of the disorders. Hence, the angle will start with the most severe disorder on the spectrum, Kanner’s autism.

Autism Spectrum


Kanner’s Autism and Rett’s Syndrome

Usually referred to as classic autism disorder, Kanner’s is the most severe as far as symptoms go. Kanner’s has three major areas of symptoms: extreme problems with social interactions, strong difficulties with imaginative play and repetitive behavior, and difficulty with verbal and non-verbal communication. Children with Kanner’s autism usually exhibit low intellectual performance. With Kanner’s, the symptoms of autism almost seem magnified, thus making it easier for doctors to diagnose accurately.

At this same point on the spectrum it is appropriate to place Rett’s Syndrome. Rett’s almost always affects girls exclusively, and many autism-like behaviors occur with Rett’s. After six to 18 months of apparently normal development, girls with Rett’s begin displaying severe problems with language, coordination, and learning. They grow more slowly than other children and usually have a small head size (microcephaly).

The Moderate Range of the Spectrum: Childhood Disintegrative Disorder and PDD-NOS

Continuing across the angle, the next PDD to appear is Childhood Disintegrative Disorder. This disorder occurs when children develop normally through age three or four, then lose the abilities they have learned, such as language skills and social skills. Like Rett’s, symptoms mirror autism disorder. Typical symptoms of Rett’s Syndrome are:

  • delay or lack of spoken language
  • impairment in nonverbal behaviors
  • inability to start or maintain a conversation
  • lack of play
  • loss of bowel and bladder control
  • loss of language or communication skills
  • loss of motor skills
  • loss of social skills
  • problems forming relationships with other children and family members

Also within the “moderate” range of the spectrum (the middle of the angle) is a disorder known as PDD-NOS (Pervasive Developmental Disorder—Not Otherwise Specified). Children with PDD-NOS don’t quite satisfy all the criteria for classic autism. They may exhibit symptoms later in life, or symptoms may not be as extreme as they are in Kanner’s autism. Some symptoms may be minor, while others may be worse. As a result, they are placed in the middle of the spectrum, where diagnosis is more difficult. Often, PDD-NOS is referred as a “catch-all term” that is used when doctors cannot pinpoint a diagnosis.

Asperger Syndrome and High Functioning Autism

Moving the wide end of the angle (the mild range), Asperger Syndrome and High Functioning Autism are seen as the most complex in presentation while being considered the mildest of the Pervasive Developmental Disorders. Asperger’s is characterized by significant difficulty with social interactions, while language skills and overall cognitive skills are relatively intact. High Functioning Autism (HFA) is not a true diagnostic term, but it describes the child who, like PDD-NOS, exhibits a milder form of classic autism. Unlike individuals with Asperger’s, children with HFA have difficulty acquiring language. They are usually able to eventually speak at an age-appropriate level. These children tend to be less socially aware than individuals with Asperger’s, also.

The autism spectrum has many different associated disorders connected to it. Disorders on the spectrum include Kanner’s Autism, Rett’s Syndrome, Childhood Disintegrative Disorder, Pervasive Developmental Disorder–Not Otherwise Specified, High Functioning Autism and Asperger Syndrome. Many times, symptoms and severity of these disorders overlap, and a visual of the spectrum can help individuals understand how they are related.

By Morgan