DSM-5 Severity Levels for Autism Spectrum Disorder
The DSM-5 defines three severity levels for Autism Spectrum Disorder based on the amount of support required in two core domains: social communication/interaction and restricted, repetitive behaviors. 1
The Three-Level System
The DSM-5 eliminated the separate diagnostic categories (Autistic Disorder, Asperger's Disorder, PDD-NOS) and created a single spectrum diagnosis with severity specified across two dimensions 1, 2:
Level 3: "Requiring Very Substantial Support"
- Social Communication: Severe deficits in verbal and nonverbal social communication skills cause severe impairments in functioning, very limited initiation of social interactions, and minimal response to social overtures from others 1
- Restricted/Repetitive Behaviors: Inflexibility of behavior, extreme difficulty coping with change, or other restricted/repetitive behaviors markedly interfere with functioning in all spheres 1
- These individuals demonstrate the lowest adaptive functioning and highest autism severity 3
Level 2: "Requiring Substantial Support"
- Social Communication: Marked deficits in verbal and nonverbal social communication skills; social impairments apparent even with supports in place; limited initiation of social interactions and reduced or abnormal responses to social overtures from others 1
- Restricted/Repetitive Behaviors: Inflexibility of behavior, difficulty coping with change, or other restricted/repetitive behaviors appear frequently enough to be obvious to the casual observer and interfere with functioning in a variety of contexts 1
- Approximately 46% of individuals in clinical samples are rated as needing Level 2 support for social communication and 49% for restricted/repetitive behaviors 3
Level 1: "Requiring Support"
- Social Communication: Without supports in place, deficits in social communication cause noticeable impairments; difficulty initiating social interactions and clear examples of atypical or unsuccessful responses to social overtures of others 1
- Restricted/Repetitive Behaviors: Inflexibility of behavior causes significant interference with functioning in one or more contexts; difficulty switching between activities; problems with organization and planning hamper independence 1
- These individuals show higher adaptation and lower autism severity compared to Levels 2 and 3 3
Critical Implementation Points
Each domain (social communication and restricted/repetitive behaviors) is rated separately, meaning an individual could theoretically have different severity levels across the two domains 1. However, clinical data suggests that individuals rarely receive discrepant ratings (e.g., Level 1 in one domain and Level 3 in another) 3.
Severity ratings demonstrate a graded pattern: Research confirms that individuals progress from higher adaptive functioning/lower autism severity at Level 1 to lower adaptive functioning/higher autism severity at Level 3 3.
Common Pitfalls to Avoid
Do not confuse severity levels with cognitive ability or adaptive functioning alone. The severity rating specifically reflects the amount of support needed due to ASD symptoms, not overall intellectual disability 4. Studies show significant discrepancies between severity classifications based on autism symptoms versus those based on cognitive skills or adaptive functioning 4.
Severity levels in young children require careful interpretation. The symptomatic manifestation in young children may not be clear or distinct enough due to age and maturation processes, making severity ratings more challenging 5.
The severity specifier must account for both current presentation and response to intervention. The DSM-5 allows for consideration of historical symptoms that may not be currently present due to intervention or development 1.