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Understanding the Autism Spectrum

Deb Levy
April 6, 2011

"She's on the spectrum."

You may have heard that phrase, but do you know what it means?  The spectrum refers to Autism Spectrum Disorders, which are typically considered to be autism, Asperger's and PDD-NOS (Pervasive Developmental Disorder - Not Otherwise Specified).  These neurobiological disorders are the three most common of the five different diagnoses that fall under the current umbrella term Pervasive Developmental Disorder (PDD).  The other two much more rare diagnoses are Childhood Disintegrative Disorder and Rett's Disorder.

Autism is characterized by impairments in three main areas:

  • social interaction
  • communication/language
  • repetitive behaviors, or 'insistence of sameness'

Autism is considered more severe in the realm of PDDs than Asperger's or PDD-NOS and may include cognitive impairment. (Learn how autism is diagnosed and the signs of autism.)

Children with Asperger's Syndrome, as described by the Autism Program at the Yale Child Study Center, display the same deficits in social interaction and their responses to the environment as children with autism, but there is no cognitive or communication impairment.  In fact, those with Asperger's Syndrome often have verbal strengths, and can talk at great length about a very specific topic - from lung diseases to the 1953 baseball season batting averages.  What they don't realize is that others aren't as keenly interested in the subject.  Some people refer to Asperger's as high-functioning autism.

PDD-NOS is sometimes referred to as 'atypical autism' or 'atypical PDD'.  It is not the same thing as PDD, which refers to a class of conditions.  The diagnosis of PDD-NOS is given when a child exhibits some of the characteristics of autism or Asperger's, but not enough to warrant a diagnosis.  Unlike autism, this diagnosis does not have its own defined set of criteria, and because the impairments are milder than in autism, children are often diagnosed with PDD-NOS at a later age than a child diagnosed with autism.

Dr. Julie Wolf, PhD, an associate research scientist and clinical psychologist at the Yale Child Study Center who works in their Autism Program, describes PDD-NOS as a catchall.  "This child has features of autism or Asperger's, but doesn't meet the strict criteria," she says.  "Maybe there are social and language impairments, but not restrictive behaviors. Or a child might have all 3, but not 6 characteristics.  It can mean a lot of different things."

In order for a child to be diagnosed correctly with PDD-NOS, the social interaction has to be impaired.  The child will show a disinterest in others around him - either through lack of eye contact, empathy, or similar interests, for example.

When are children diagnosed?

It varies, depending on the child.  Some clinicians and parents see signs as early as infancy, especially in the case of twins when delays are more obvious as compared to a typically developing child.  Yet with Asperger's or PDD-NOS, because the impairments aren't always as severe, a diagnosis may not be made until grade school.  The symptoms, however, are usually present before age three.

Before you get too attached to these definitions, it is important to note that the diagnoses will change in May of 2013 when the American Psychiatric Association (APA) publishes the DSM-5, its updated diagnostic and statistical manual of mental disorders.  There will no longer be distinct diagnoses of autism, Asperger's and PDD-NOS.  Instead, all of these characteristics and behaviors will be labeled Autism Spectrum Disorder (ASD).

The three main categories of impairments will become two: social/communication deficits, and fixated interests and repetitive behaviors.  And clinicians will determine the proper severity from level 1 'requiring support' to level 3 'requiring very substantial support.'  (Level 2 is indicated as 'requiring substantial support.')

Why the change?

As the APA website states, "Previously, the criteria were equivalent to trying to 'cleave meatloaf at the joints.'"  Simply, it's not easy to distinguish properly between the various disorders.

According to the APA, distinctions between autism, Asperger's and PDD-NOS were found to be inconsistent over time, and the new criteria were created to ensure that individual clinicians could make a diagnosis more reliably and with validity.  The APA also feels that a single spectrum disorder better reflects the current state of knowledge about the pathology and clinical presentation of the disorder.

For parents and nannies who know that trying to raise and advocate for kids on the spectrum is even harder than nailing down a diagnosis, hopefully there is some comfort in knowing that the greater world is seeking a better understanding of it all.

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