Diagnostic Criteria for Atypical Autism (Autism Spectrum Disorder)
Atypical autism falls under the broader diagnosis of Autism Spectrum Disorder (ASD), characterized by persistent deficits in social communication and interaction, along with restricted and repetitive patterns of behavior, interests, or activities that cause significant impairment in functioning.
Core Diagnostic Criteria
1. Social Communication and Social Interaction Deficits
- Deficits in social-emotional reciprocity
- Deficits in nonverbal communicative behaviors used for social interaction
- Difficulties developing, maintaining, and understanding relationships 1
2. Restricted, Repetitive Patterns of Behavior, Interests, or Activities
- Stereotyped or repetitive motor movements, use of objects, or speech
- Insistence on sameness, inflexible adherence to routines
- Highly restricted, fixated interests that are abnormal in intensity or focus
- Hyper- or hyporeactivity to sensory input 1
3. Additional Requirements
- Symptoms must be present in early developmental period (though may not become fully manifest until social demands exceed limited capacities)
- Symptoms cause clinically significant impairment in social, occupational, or other important areas of functioning
- Disturbances are not better explained by intellectual disability or global developmental delay 1
Specific Features of Atypical Autism
Atypical autism (previously termed PDD-NOS - Pervasive Developmental Disorder Not Otherwise Specified) encompasses subthreshold cases on the autism spectrum where:
- Full criteria for explicitly defined autism spectrum disorders are not met
- The individual has problems in social interaction
- The individual has some difficulties in communication or restricted patterns of behavior 2
Individuals with atypical autism are typically:
- Less impaired than those with classic autism
- Have fewer repetitive behaviors
- Generally have a better prognosis 2
Early Markers (12-24 months)
Strong evidence supports the following as early markers of ASD:
- Impairments in social attention and social communication
- Atypical object use
- Reduced levels of:
- Response to name
- Eye contact
- Joint attention
- Nonverbal communication
- Social reciprocity 2
Additional potential markers include:
- Abnormal body movements
- Temperament dysregulation
- Lower positive affect
- Higher negative affect
- Difficulty controlling behavior
- Lower sensitivity to social reward cues 2
Diagnostic Evaluation Process
A comprehensive diagnostic evaluation should include:
Standardized diagnostic instruments:
- Autism Diagnostic Observation Schedule-Second Edition (ADOS-2)
- Autism Diagnostic Interview-Revised (ADI-R) 1
Multidisciplinary assessment:
- Direct behavioral observation
- Detailed developmental history
- Cognitive assessment
- Language assessment (receptive and expressive) 1
Screening for comorbid conditions:
- Anxiety disorders
- Depression
- ADHD
- Learning disabilities 1
Medical evaluation:
- Physical examination
- Hearing screening
- Genetic testing when indicated 1
Common Diagnostic Challenges
- Overlooking diagnosis in individuals with average or above-average intelligence
- Misattributing social difficulties to shyness or introversion
- Focusing only on strengths while missing functional impairments
- Overlooking diagnosis in females who may present differently
- Waiting for language delays that may not appear in some cases 1
Clinical Implications
Early identification of ASD is crucial as it:
- Enables early intervention, which enhances developmental outcomes
- Allows for implementation of specialized interventions tailored to specific needs
- Provides families access to appropriate support services and resources 3
However, clinicians should be aware of potential risks including:
- Labeling and stigmatization
- Possibility of overdiagnosis or misdiagnosis
- Emotional challenges for families during the diagnostic process 3
The high prevalence of comorbid conditions (depression 20%, anxiety 11%, sleep difficulties 13%, epilepsy up to 21% with co-occurring intellectual disability) highlights the importance of comprehensive evaluation and management 4.
When atypical features are present, careful assessment is needed to distinguish ASD from other conditions and to identify the specific pattern of strengths and challenges to guide intervention planning.