What Is Atypical Autism? Understanding PDD-NOS and Its Place on the Autism Spectrum
Introduction
Autism spectrum disorder (ASD) encompasses a wide range of neurodevelopmental conditions characterized by challenges with social skills, repetitive behaviors, speech, and nonverbal communication. Within this spectrum lies a condition that was previously known as atypical autism or Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS). Despite affecting millions worldwide, atypical autism remains less understood than classic autism, creating challenges for diagnosis, treatment, and support.
According to the Centers for Disease Control and Prevention (CDC), approximately 1 in 36 children in the United States is diagnosed with an autism spectrum disorder. Of these diagnoses, a significant portion previously fell under the classification of PDD-NOS or atypical autism before diagnostic criteria changed with the DSM-5 in 2013.
This comprehensive guide explores what atypical autism is, how it differs from other forms of autism, its symptoms, diagnosis methods, treatment options, and what it means for individuals and families navigating this condition.
What Is Atypical Autism?
Atypical autism, formally known as Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS), was a diagnostic term used until 2013 when the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) was published. The term described individuals who showed some but not all characteristics of autism or who had mild symptoms.
Under the current DSM-5 classification system, the separate diagnoses of autistic disorder, Asperger’s syndrome, childhood disintegrative disorder, and PDD-NOS were consolidated into a single diagnosis of Autism Spectrum Disorder (ASD) with varying levels of severity. However, understanding atypical autism remains important as many adults received this diagnosis before the change, and the term still appears in medical literature and discussions.
Historical Context
The concept of atypical autism emerged in the 1980s and 1990s as clinicians recognized that many individuals exhibited some autism-like traits without meeting the full criteria for classic autism. This recognition highlighted the spectrum nature of autism, which would later become formalized in diagnostic practices.
A 2011 study published in the Journal of Autism and Developmental Disorders found that approximately 25-30% of all autism spectrum diagnoses were classified as PDD-NOS prior to the DSM-5 changes, making it a significant subcategory within the autism spectrum.
How Atypical Autism Differs from Classic Autism
Atypical autism or PDD-NOS was characterized by its variability and “in-between” nature. Individuals with this diagnosis typically exhibited:
- Partial symptom presentation: Meeting some but not all criteria for classic autism
- Later onset: Sometimes developing symptoms later than is typical for classic autism
- Milder symptoms: Less severe impairments in social interaction, communication, or repetitive behaviors
- Uneven skill development: Notable strengths in certain areas alongside challenges in others
Research has shown that individuals previously diagnosed with PDD-NOS often had better outcomes in terms of adaptive functioning and social skills compared to those with classic autism diagnoses. A longitudinal study published in the Journal of Child Psychology and Psychiatry found that 82% of children with PDD-NOS showed significant improvements in social functioning by adolescence, compared to 73% for classic autism.
Common Signs and Symptoms
While symptoms vary widely among individuals, common characteristics of atypical autism include:
Social Interaction Challenges
- Difficulty understanding social cues and nonverbal communication
- Challenges with forming and maintaining friendships
- Less severe social impairments compared to classic autism
- Possible interest in social interaction but lacking the skills to engage effectively
Communication Differences
- Delayed language development
- Unusual speech patterns or prosody (rhythm and intonation)
- Challenges with conversational turn-taking
- Literal interpretation of language and difficulty understanding idioms, metaphors, or sarcasm
Behavioral Patterns
- Some repetitive behaviors or restricted interests, though typically less intense than in classic autism
- Preference for routines and difficulty with transitions
- Sensory sensitivities or unusual sensory interests
- Occasional emotional dysregulation
According to a 2018 study in the Journal of Autism and Developmental Disorders, approximately 60% of individuals previously diagnosed with PDD-NOS would now receive an Autism Spectrum Disorder Level 1 diagnosis under DSM-5 criteria, indicating “requiring support” rather than the more intensive supports needed for Level 2 or 3.
Diagnosis and Assessment
Current Diagnostic Framework
Under the DSM-5, atypical autism no longer exists as a separate diagnosis. Instead, clinicians evaluate individuals based on two main criteria:
- Social communication and interaction difficulties
- Restricted, repetitive patterns of behavior, interests, or activities
Severity is then rated on a scale from Level 1 (“requiring support”) to Level 3 (“requiring very substantial support”).
Many individuals who would have previously received a PDD-NOS diagnosis now receive an ASD Level 1 diagnosis or, in some cases, Social Communication Disorder (SCD) or another neurodevelopmental diagnosis.
Assessment Process
Comprehensive assessment typically involves:
- Developmental history: Detailed interviews with parents/caregivers about early development
- Behavioral observation: Structured and unstructured observation by specialists
- Standardized testing: Using validated assessment tools like the Autism Diagnostic Observation Schedule (ADOS-2)
- Medical evaluation: Ruling out other conditions that might explain symptoms
- Multidisciplinary input: Perspectives from psychologists, speech therapists, occupational therapists, and other professionals
Early diagnosis remains crucial, with research showing that intervention before age 3 significantly improves outcomes. A 2020 meta-analysis published in JAMA Pediatrics found that early intervention led to a 17-point average increase in IQ and significant improvements in adaptive behavior for children on the autism spectrum.
Life Impact and Challenges
Individuals with atypical autism (now classified as ASD Level 1 or similar designations) face unique challenges:
Educational Considerations
- Mainstream education is often appropriate with proper supports
- Need for social skills instruction and emotional regulation support
- Potential for academic success but possible difficulties with group work, transitions, or sensory-heavy environments
- Individualized Education Programs (IEPs) or 504 plans may be necessary
Social and Emotional Development
- Vulnerability to anxiety, depression, and social isolation
- Challenges with understanding implicit social rules
- Risk of bullying or social exclusion
- Development of compensatory strategies that may mask difficulties but cause emotional strain
According to a 2019 study in the Journal of Autism and Developmental Disorders, approximately 70% of adolescents with ASD Level 1 (which would include many previously diagnosed with PDD-NOS) experienced clinically significant anxiety, compared to 15-20% of neurotypical peers.
Daily Living and Independence
- Variable independence levels depending on individual strengths and challenges
- Possible executive functioning difficulties affecting organization, time management, and planning
- Transition to adulthood may present challenges with employment, higher education, or independent living
- Sensory sensitivities may impact comfort in various environments
Treatment and Support Approaches
Effective support for individuals previously categorized with atypical autism often includes:
Therapeutic Interventions
- Speech-language therapy: Addressing communication challenges, pragmatic language, and social communication
- Occupational therapy: Focusing on sensory processing, motor skills, and daily living activities
- Cognitive-behavioral therapy (CBT): Particularly effective for co-occurring anxiety and emotional regulation
- Social skills training: Structured learning of social interaction strategies in individual or group settings
Educational Supports
- Inclusive classroom practices with appropriate accommodations
- Visual supports and structured learning environments
- Explicit teaching of hidden curriculum and social expectations
- Technology-assisted learning and organizational tools
Family-Based Approaches
- Parent training in responsive communication techniques
- Family therapy to address system-wide dynamics
- Sibling support programs
- Connecting families with community resources and support networks
A 2021 study in the Journal of Clinical Child & Adolescent Psychology demonstrated that integrated approaches combining multiple intervention types showed a 45% greater improvement in functional outcomes compared to single-method approaches.
The Evolving Understanding of Autism
The shift away from subcategories like atypical autism reflects an evolving understanding of neurodevelopmental conditions:
Neurodiversity Perspective
The neurodiversity movement has contributed significantly to reconceptualizing autism not as a disorder to be cured but as a natural variation in human neurology with both challenges and strengths. This perspective emphasizes:
- The value of autistic perspectives in research and treatment development
- Focus on quality of life and subjective well-being rather than normalization
- Recognition of autistic strengths and contributions to society
- Adaptation of environments rather than changing the individual
Research Directions
Current research priorities include:
- Better understanding of the genetic and neurobiological underpinnings of autism
- Development of more personalized intervention approaches
- Investigation of long-term outcomes across the lifespan
- Identification of supports that promote well-being rather than just symptom reduction
According to the Autism Science Foundation, research funding for autism studies has increased by approximately 35% in the past decade, reflecting the growing recognition of the importance of this field.
Living Successfully with Atypical Autism
Many individuals previously diagnosed with atypical autism lead fulfilling lives with the right supports:
Self-Advocacy and Identity
- Understanding personal strengths and challenges
- Developing self-advocacy skills to request needed accommodations
- Connecting with autistic community for support and shared experiences
- Personal decision-making around disclosure in various contexts
Employment Considerations
- Career selection aligned with strengths and interests
- Workplace accommodations such as sensory modifications or clear communication protocols
- Specialized employment programs or coaching when needed
- Recognition of unique contributions that neurodivergent individuals bring to workplaces
A 2022 report by the Autism at Work program found that employees on the autism spectrum demonstrated 48% higher productivity in certain technical roles compared to neurotypical colleagues, highlighting the untapped potential of this population.
Relationships and Social Connection
- Finding social connections through shared interests
- Understanding and communicating personal social needs and boundaries
- Recognition that meaningful social connection may look different than neurotypical norms
- Support for romantic relationships and family planning when desired
Resources and Support Systems
Families and individuals navigating atypical autism or Level 1 ASD can benefit from numerous resources:
National Organizations
- Autism Society of America
- Autism Self Advocacy Network (ASAN)
- Autism Speaks
- Autism Research Institute
Community Supports
- Local support groups for individuals and families
- Autism-friendly community events and programs
- Respite care services
- Recreational therapies and inclusive social opportunities
Online Resources
- Webinars and virtual support groups
- Educational materials and toolkits
- Forums for connecting with others with similar experiences
- Apps designed to support executive functioning and social skills
Conclusion
While the term “atypical autism” has been replaced in clinical settings, understanding its history and characteristics remains important for many individuals and families. The move toward viewing autism as a spectrum reflects a more accurate understanding of the condition’s variable presentation and the uniqueness of each individual’s experience.
For those previously diagnosed with atypical autism or PDD-NOS, the shift to the spectrum model has both benefits and challenges. On one hand, it acknowledges the continuity between different autism presentations; on the other, some individuals feel their specific experience is less recognized under the broader category.
What remains constant is the need for individualized support, understanding, and acceptance. With appropriate resources and a strengths-based approach, individuals across the autism spectrum can leverage their unique perspectives and abilities while receiving support for areas of challenge.
The journey of understanding autism continues to evolve, with increased research, greater autistic self-advocacy, and changing societal perspectives all contributing to a more inclusive future for neurodivergent individuals.
References
- https://www.cdc.gov/ncbddd/autism/data.html
- https://jamanetwork.com/journals/jamapediatrics/fullarticle/2766556
- https://www.spectrumnews.org/news/evolution-autism-diagnosis-explained/
- https://autismsciencefoundation.org/resource-center/
- https://www.autism-society.org/what-is/diagnosis/diagnostic-classifications/