Autism spectrum disorder (ASD) is a complex neurodevelopmental condition that impacts how a person communicates, interacts, behaves, and learns. In recent years, our understanding of autism has evolved dramatically. One major change is the phasing out of previously separate subtypes like Asperger’s syndrome and pervasive developmental disorder-not otherwise specified (PDD-NOS) – now referred to as “atypical autism.”
While the diagnostic criteria have changed, the challenges faced by people with atypical autism have not. Understanding this formerly distinct subtype provides key insights into the diversity of the autism spectrum.
What Exactly is Atypical Autism?
Up until 2013, autism subtypes like Asperger’s syndrome, PDD-NOS, and “classic” autistic disorder were diagnosed separately using criteria listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).1
PDD-NOS was a diagnosis given to those who met some but not all criteria for autistic disorder. Specifically, PDD-NOS was characterized by:2
- Impairments in social interaction
- Impairments in communication
- Repetitive behaviors and restricted interests
However, symptoms were less severe than those required for an autistic disorder diagnosis. Individuals had to meet at least two of the above criteria, with onset in early childhood.
The release of the DSM-5 in 2013 brought a single umbrella diagnosis of ASD, encompassing the various subtypes.3 Rather than lists of criteria, autism is now conceptualized as a spectrum disorder with different levels of support needs.
This had advantages in acknowledging the diversity of autism traits. However, it also eliminated longstanding subcategories like PDD-NOS.
Why the Definition Changed
Previously, Asperger’s syndrome and PDD-NOS were viewed as “milder” forms of autism. But in reality, disability levels can vary widely within and across subtypes. There are those with PDD-NOS who face major impairments.4
The DSM-5 addressed this by introducing 3 levels of support:
- Level 1: Low support needs. Some challenges with social skills, communication, organization.
- Level 2: Moderate support needs. Marked challenges in social skills, communication, behavior.
- Level 3: High support needs. Severe deficits in verbal and nonverbal skills cause major impairment.
This helps classify autism based on support needs rather than just outward symptoms. Those with PDD-NOS may fall anywhere along this spectrum.
Additionally, the DSM-5 recognized autism as a multifaceted combination of traits. Rigid criteria failed to capture the true diversity of symptoms and abilities.
The spectrum model aims to represent this heterogeneity through personalized ratings of severity across two core symptom domains:5
- Persistent deficits in social communication/interaction
- Restricted/repetitive behaviors, interests, or activities
This more flexible approach helps provide a nuanced profile of each individual’s strengths and challenges.
Characteristics of Atypical Autism
Though no longer a separate diagnosis, understanding PDD-NOS provides insights into the autism spectrum. Some common traits include:6
Social Communication Challenges
- Delayed language development
- Minimal facial expressions or gestures
- Poor eye contact
- Lack of pretend play
- Does not share interests/achievements
- Limited interest in making friends
Restricted & Repetitive Behaviors
- Repetitive speech or movements
- Rigid adherence to routines
- Highly restricted interests
- Unusual sensory reactions
Unlike autistic disorder, those with PDD-NOS often have milder symptoms in these areas. However, they still cause significant impairment in school, work, and relationships.
It is a myth that high-functioning autism and PDD-NOS are easy or require little support. In fact, atypical presentations often fly under the radar, leading to lack of services.
How Atypical Autism is Diagnosed and Treated
Since PDD-NOS is no longer a formal diagnosis, how are cases of atypical autism identified and supported today?
Diagnosis
Diagnosing autism is now based on the presence and severity of core symptom domains in the DSM-5. A comprehensive evaluation involves:7
- Developmental screening
- Autism-specific behavioral assessments
- IQ and skills testing
- Speech/language assessment
- Occupational therapy evaluation
- Medical exam to rule out conditions with similar symptoms
Clinicians synthesize results to determine if criteria are met for ASD. They also gauge the severity of social communication deficits and restrictive/repetitive behaviors.
Treatment
Interventions are tailored to the individual’s strengths, challenges, and support needs. Common approaches include:
- Applied behavior analysis (ABA): Uses positive reinforcement to build communication, social, academic, and adaptive skills.
- Speech therapy: Improves verbal and nonverbal communication abilities.
- Occupational therapy: Focuses on sensory integration, motor skills, and activities of daily living.
- Cognitive behavioral therapy: Helps manage anxiety, social challenges, and restrictive behaviors.
- Social skills training: Teaches strategies for building relationships and navigating social situations.
- Medications: May be used to treat co-occurring symptoms like irritability and anxiety.
Regardless of an atypical vs. classic presentation, personalized treatment is key. An interdisciplinary team works closely with families to provide comprehensive support.
Navigating the Diverse Landscape of Autism
Refining our understanding of autism subtypes like PDD-NOS enriches our view of the spectrum as a whole. While criteria and terminology evolve, each person’s unique blend of strengths and challenges remain.
Subthreshold presentations emphasize the need to look beyond diagnostic labels. Support should be tailored to individual needs. Those with atypical autism deserve access to services and acceptance as much as anyone else.
Unlocking the mysteries of this diverse spectrum disorder guides us to be more responsive, compassionate, and empowering. With the right supports, those with atypical autism can also achieve full potential.
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References
- Ousley, O., & Cermak, T. (2014). Autism spectrum disorder: Defining dimensions and subgroups. Current Developmental Disorders Reports, 1(1), 20–28. https://doi.org/10.1007/s40474-013-0003-1
- Huerta, M., Bishop, S. L., Duncan, A., Hus, V., & Lord, C. (2012). Application of DSM-5 criteria for autism spectrum disorder to three samples of children with DSM-IV diagnoses of pervasive developmental disorders. American Journal of Psychiatry, 169(10), 1056–1064. https://doi.org/10.1176/appi.ajp.2012.12020276
- Regier, D. A., Kuhl, E. A., & Kupfer, D. J. (2013). The DSM-5: Classification and criteria changes. World Psychiatry, 12(2), 92–98. https://doi.org/10.1002/wps.20050
- Kim, Y. S., Fombonne, E., Koh, Y. J., Kim, S. J., Cheon, K. A., & Leventhal, B. L. (2014). A comparison of DSM-IV pervasive developmental disorder and DSM-5 autism spectrum disorder prevalence in an epidemiologic sample. Journal of the American Academy of Child & Adolescent Psychiatry, 53(5), 500–508. https://doi.org/10.1016/j.jaac.2013.12.021
- Guthrie, W., Swineford, L. B., & Wetherby, A. M. (2013). Comparison of DSM-IV and DSM-5 factor structure models for toddlers with autism spectrum disorder. Journal of the American Academy of Child & Adolescent Psychiatry, 52(8), 797–805. https://doi.org/10.1016/j.jaac.2013.05.004
- Hodges, H., Fealko, C., & Soares, N. (2020). Autism spectrum disorder: Definition, epidemiology, causes, and clinical evaluation. Translational Pediatrics, 9(Suppl 1), S55–S65. https://doi.org/10.21037/tp.2019.09.09
- National Health Service Foundation Trust. (n.d.). What is autism and how do we make a diagnosis in the new era of DSM-5 and ICD-11? https://www.nottinghamshirehealthcare.nhs.uk/download.cfm?doc=docm93jijm4n3321.pdf&ver=9920