What Is the Difference Between Aspergers and PDD-NOS?

Asperger syndrome therapies

What is the difference between Aspergers and PDD-NOS? This pressing question is difficult to address, but the answer may derive from how we define communication. The process begins with looking at the diagnostic criteria for each condition.

DSM IV Criteria

The DSM IV introduced the Asperger syndrome as a diagnosis in 1994, making it the newest of the five pervasive developmental disorders. There are five developmental disorders in the pervasive developmental disorder classification, also referred to as the autism spectrum.

Each of the disorders must have some things in common in order for them to fit into the spectrum, but each subset of the autism spectrum meets specific criteria for proper classification. This approach to organizing the conditions helps to create appropriate treatment plans for individual cases.


A diagnosis of PDD-NOS indicates that the individual has many of the signs of autism while not meeting the criteria of Retts, childhood disintegrative disorder, classical autism, or Aspergers. The symptoms are pronounced enough to interfere with the person's ability to function normally on a daily basis.

Many PDD-NOS cases are very high functioning, but some are low functioning, especially if the individual has a dual diagnosis. Just as the autism spectrum covers a wide range of abilities, so does the cases of PDD, not otherwise specified. Some assert that the diagnosis should be replaced with high functioning autism, but this works on the assumption that all individuals with the diagnosis are high functioning though this is not always the case when there is a comorbid condition.

In addition, some assert that Aspergers is high functioning autism, but it is a distinct condition that does not meet the same criteria as classical autism in spite of its similarities. Determining the difference between PDD-NOS and AS begins with exploring the diagnostic criteria.

What Is the Difference Between Aspergers and PDD-NOS

What is the difference between Aspergers and PDD-NOS? The question may be addressed by looking at the factors that make Aspergers unique from the other pervasive developmental disorders, according to the DSM IV.

  • Communication
  • Cognitive functioning


Two areas that make Aspergers unique among the five pervasive developmental disorders are communication and cognition. Individuals diagnosed with Aspergers syndrome do not display the marked delay in language acquisition. Individuals falling into PDD not otherwise specified have delayed speech, and when language develops, it often is not functional. This topic becomes complicated when as we consider how communication is defined. Some consider communication to be the use of functional language. In other words, the individual uses words, facial expressions and gestures to get a behavioral response from another person. Asking for a toy, saying, "I'm hungry," and pointing to objects of interest are examples of functional communication.

Some define communication as sharing experiences and thoughts. This is more complex in that the person communicating is trying to make the thoughts in another person's mind match their own. For example, "The rustling of the leaves sounded like crashing ocean waves." The language communicates an experience by creating an auditory representation. It functions to share an experience rather than to control the environment or encourage someone else to provide a behavioral response.

A person with Aspergers typically has an impressive vocabulary that he can use on a functional level, but communication becomes confusing when language is used to communicate experiences. This is especially troublesome when it comes to humor, metaphors and figurative language. These must be taught deliberately and systematically.


Cognitive development appears to be normal or above average for individuals with Aspergers. This distinction in the DSM-IV is as complicated as the issues with communication. Individuals diagnosed with PDD-NOS do not fall into any of the four other pervasive developmental disorders. Some may not have deficits in cognition displayed by individuals with classical autism, Retts or childhood disintegrative disorder. The lack of cognitive delay is not enough for them to be diagnosed with AS because they display the marked delay in language development.

High Functioning Autism and AS

Web MD notes that many professionals consider high functioning autism and AS to be the same or very similar. Although the symptoms pose challenges, the individuals have normal or above average intelligence. The designation "high functioning autism" is confusing because Aspergers is not autism per se. It is one of the five pervasive developmental disorders. The group of disorders is also referred to as the autism spectrum (ASD).


People have a natural drive to create order, and this often involves using labels to classify individuals. While the specific labels can help the treatment team determine the best strategies to use, it is probably better to put more energy into treating the individual rather than trying to categorize him.

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What Is the Difference Between Aspergers and PDD-NOS?