Autistic Disorder- Aspergers Disorder and PDD-NOS Similarities and Differences

Autism Spectrum Disorder (ASD), is a name that categorizes a number of disorders that are associated with behavioural, social and developmental problems. ASD is referred to as a “spectrum” disorder because it encompasses a wide variation in the severity and type of symptoms experienced by those with ASD (NIMH, 2018). Thus, ASD is associated with more than just Autistic Disorder, it also includes: Asperger’s Disorder, Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS), Rett Syndrome and Childhood Disintegrative Disorder (CDD) (McPartland & Volkmar, 2012). Due to the wide variations found within ASD, it is important to understand the similarities and differences in the disorders that make up ASD as this ensures that professionals, parents, teachers and others affected by ASD understand the uniqueness of the disorder at hand. This provides vital information that can help place a student or child on the spectrum, allowing for the most appropriate strategies, programs and interventions to be used in order to ensure success within the classroom and to increase quality of life. Therefore, this paper will focus on understanding the similarities and differences within Autistic Disorder, Asperger’s Disorder and PDD-NOS as a means to understand how and why they are grouped under the umbrella of Autism Spectrum Disorder.

As previously mentioned before, ASD is not defined by a common set of behaviours but is rather a combination of diagnostic categories that range in their type of symptoms and severity due to the array of disorders grouped within ASD.  As outlined by the

Diagnostic and Statistical Manual of Mental Disorders

(DSM-IV), a guide created by the American Psychiatric Association (2013) and

Special Education in Canada

(Edmunds and Edmunds, 2018), those diagnosed with ASD have these common features:

  1. Difficulty with communication and interaction with other people. For instance, those with ASD often struggle to understand and communicate their own feelings as well as other people’s feelings.
  2. Restricted interests and repetitive behaviour, such as, the need to knock four times after closing a door.
  3. Symptoms that hurt the person’s ability to function properly in school, work and other areas of life.

One may note that the first two common features tend to present concrete symptoms while the last symptom tends to offer ambiguity as to what may hinder a person’s ability to function properly within society. This tends to be the area in which we see the uniqueness and variety of ASD come through.

Autistic Disorder, also known as “classical” autism, is defined as a “neurodevelopmental disorder that impacts the brain development” (Autism Canada, 2018). This delay in neurodevelopment often causes individuals with autism to have difficulties with communication, social interactions, and repetitive behaviours (Autism Canada, 2018). Thus, one might assume that ASD and Autistic disorder are synonymous with one another as Autistic Disorder tends to follow the common features outlined by the DSM-IV the closest. Beyond the common features, Autistic Disorder has many other challenges associated with it. For instance, it is a co-occurring medical condition that is often accompanied with conditions such as epilepsy, sleep disorders, gastrointestinal abnormalities, as well as, depression and anxiety that can often perpetuate the already present symptoms of the disorder (Autism Canada, 2018). For instance, a student with Autistic Disorder that has difficulty with social interactions may already experience a high volume of stress and anxiety but add in other elements such as epileptic episode and the potential for social discrimination increases, this in turn may cause further stress and anxiety resulting in a perpetuated cycle of symptoms.

Although, Autistic Disorder, tends to be the most common and widely known disorder on the spectrum, other disorders are just as prominent. Asperger’s Disorder, is often recognized as a “high functioning” form of autism and can often go misdiagnosed or even unrecognized and therefore undiagnosed up until adulthood (Ontario Adult Autism, 2018). Those with Asperger’s are thought to be high functioning as they tend to develop language normally and are often lack or have mild cognitive delays (Ontario Adult Autism, 2018). However, those with Asperger’s will still have symptoms such as difficulty in social interactions as well as fine and gross motor coordination. They may struggle with changes in routines, sensory overload, conflict and an inability to understand emotions and social cues (Rudy, 2017). However, it is interesting to note that those with Asperger’s may demonstrate an extreme passion or proficiency in one or two topics and/ or skills (Rudy, 2017). For instance, the T.V. show


follows the life of a boy named Sam who has high functioning autism. Sam is extremely knowledgeable about Antarctica and penguins, so much so, that he is only allowed to speak about the topics three times a day before it is no longer “socially acceptable” as deemed by his girlfriend. In many ways, Sam is completely functional in society, as he is a straight ‘A’ student, holds a job and a romantic relationship but in other aspects, displays the common symptoms of ASD, such as, his extreme passion for Antarctica, his sensitivity to sounds and his inability to accommodate changes in routine. Those with Asperger’s can also depict social extremes with some being painfully shy while others excessively outgoing. An example of this is my friend Jay, who runs track and field. Jay in many aspects is a normal kid that has a job, hobbies and a passion for running but despite his ability to function within society, he still struggles to create and maintain genuine relationships because of his over excitement in social situations. I believe that it is in high functioning cases such as Jay’s that ASD can go undetected well up into the adult years.

The last disorder we will examine is Pervasive Developmental Disorder- Not Otherwise Specified.  PDD-NOS, as a diagnosis remains relatively new, only dating back about 15 years (Autism Speaks, 2016). As a result, some educators and physicians may not be familiar with the term or even use it correctly. In the past, the term “pervasive developmental disorders” and “autism spectrum disorders” were used interchangeably. Now PDD-NOS is now the diagnosis applied to children or adults who are on the autism spectrum but do not fully meet the criteria for another ASD such as Asperger Disorder or Autistic Disorder (Autism Speaks, 2016). Similar to other forms of ASD, PDD-NOS is largely defined by significant challenges in social and language development. However, it differs in that it is often referred to by developmental health professors as “subthreshold autism”, meaning that it is often the diagnosis that is used for someone that has some but not all characteristics of autism (Autism Speaks, 2016). For instance, a person may have severe deficits socially but lack or have mild deficits in another common feature of autism such as repetitive behaviours. Thus, a person with PDD-NOS can fall into one of three subgroups: A high functioning group, with symptoms that overlap with Asperger’s Disorder but differing in a mild impairment in language and cognitive development (Autism Speaks, 2016). A second group with symptoms that resemble autistic disorder but do not fully meet the diagnostic criteria (Autism Speaks, 2016). A third group whose symptoms meet all the diagnostic criteria for autistic disorder but whose stereotypical repetitive behaviours are mild (Autism Speaks, 2016). PDD-NOS, wonderfully demonstrates the spectrum within autism as it demonstrates the variability, severity as well as overlap of the symptoms of autism while also demonstrating the traits unique to each disorder.

Thus, in examining Autistic Disorder, Asperger’s Disorder and PDD-NOS, one can see that all three disorders share commonalities in that they are products of developmental delays.  All share similarities in the diagnostic criteria set by the DSM-IV with slight variances that make them unique to one another. For instance, all three disorders impede on the ability to socialize with others. Autistic Disorder can often result in a mild or complete lack of emotional or social understanding,  Asperger’s Disorder can form extreme cases of over socialization as seen in Jay’s story, while PDD-NOS can share characteristics of both Autistic Disorder and Asperger’s Disorder. However, it is important to remember that just like any other learning disorder or exceptionality, there are commonalities within the disorders as well as differences. Thus, it is the shared common features that place these three disorders under the umbrella of Autism Spectrum Disorder but it is the unique displays, variations and severities that also makes them their own disorder. As educators, it is important to understand that although there are commonalities within a learning disability or exceptionality, there are also going to be differences that we need to look out for. If we are able to do that, then we will be more in tune with the needs of our students and can provide them with the appropriate supports, interventions and programming necessary for success in and out of the classroom.


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  3. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. (2013). American Psychiatric Association.
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    Special Education in Canada


    Third Edition.

    Don Mills, Ontario: Oxford University Press.
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    Neurobiology Of Psychiatric Disorders

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