Autism

Guide

Neurodevelopmental Disorders & Learning Differences

Guide

Types of Autism Spectrum Disorder: Levels, Traits & Former Diagnoses Explained

Authored by: The DrSensory Editorial Team

Reviewed by: 🛡️ DrSensory Clinical Review Board

Last updated: June 2026

All medical content on this page has been reviewed and approved by licensed Doctors on the DrSensory Clinical Review Board. Our reviewers follow strict editorial standards and ensure alignment with current APTA guidelines, evidence-based practice, and orthopedic rehabilitation protocols.

Key Takeaways

Autism Spectrum Disorder (ASD) is a single diagnosis that covers a wide range of presentations, classified by the severity of symptoms and the level of support a person needs.
The DSM-5 organizes autism into three levels: Level 1 (requiring support), Level 2 (requiring substantial support), and Level 3 (requiring very substantial support).
Before the DSM-5, autism-related conditions were diagnosed separately as Classic Autism (Autistic Disorder), Asperger's Syndrome, and PDD-NOS; today all are recognized as part of ASD.
Asperger's Syndrome is no longer a standalone diagnosis and is now considered part of Level 1 ASD, though many people still identify with the term and it remains recognized in education and support communities.
Identifying a person's type or level of autism helps families and professionals choose the right interventions, therapies, and educational accommodations through personalized care plans.

Types of ASD?
Differences with ASD?
Levels 1, 2, & 3 of ASD?
Traits or Symptoms for Each Type of Autism?

14 min read

What is Asperger’s Syndrome and how is it different from other types of autism?
What does PDD-NOS mean and is it still diagnosed today?
What is Classic Autism (Autistic Disorder)?

What are the different types of autism spectrum disorder (ASD)?

Autism Spectrum Disorder (ASD) is classified as a single diagnosis but includes a wide range of presentations based on the severity of symptoms and support needs. The three main types of autism, often referred to in clinical and educational settings, include:

Level 1 (Mild or High-Functioning Autism) – Individuals need some support and may struggle with social interaction and organization.
Level 2 (Moderate Autism) – Individuals require substantial support and often face challenges with communication and behavior.
Level 3 (Severe Autism) – Individuals need very substantial support and may be nonverbal or have severe sensory and behavioral differences.

These “levels” help professionals develop personalized treatment plans and support strategies.

What is the difference between classic autism, Asperger’s syndrome, and PDD-NOS?

Before the DSM-5 grouped all autism-related conditions into Autism Spectrum Disorder (ASD), they were diagnosed separately:

Classic Autism (Autistic Disorder) – Characterized by significant language delays, social and behavioral challenges.
Asperger’s Syndrome – Individuals often have average to high intelligence and no significant speech delay but struggle with social skills and sensory sensitivities.
Pervasive Developmental Disorder – Not Otherwise Specified (PDD-NOS) – A diagnosis for individuals who showed some autism traits but didn’t meet the full criteria for other subtypes.

Today, these are all recognized as part of ASD, reflecting the spectrum nature of autism.

What is Level 1, Level 2, and Level 3 autism?

The DSM-5 categorizes autism by levels of support needed, helping clarify the range of challenges an individual may face:

Level 1 Autism (Requiring Support): May appear high-functioning; needs help with social interactions and organization.
Level 2 Autism (Requiring Substantial Support): More noticeable difficulties with communication, behavior, and adaptability.
Level 3 Autism (Requiring Very Substantial Support): Severe impairments in verbal and nonverbal communication, with strong reliance on caregivers or full-time support.

These levels are essential for designing custom care plans, therapies, and educational accommodations.

Are there specific traits or symptoms for each type of autism?

Yes, each type or level of autism is associated with certain traits, though individuals may vary:

Level 1 (Mild ASD): Trouble with social cues, inflexible thinking, prefers routines, may appear shy or socially awkward.
Level 2 (Moderate ASD): Noticeable speech delays, difficulty coping with change, and repetitive behaviors like hand-flapping.
Level 3 (Severe ASD): Nonverbal or limited communication, extreme sensory sensitivities, and frequent meltdowns or shutdowns.

Understanding these differences helps families and professionals choose the right interventions and support systems.

What is Asperger’s Syndrome and how is it different from other types of autism?

Asperger’s Syndrome was once a separate diagnosis used for individuals on the autism spectrum who had average to above-average intelligence and no significant language delays. People with Asperger’s often struggle with social interaction, exhibit narrow interests, and may have sensory sensitivities, but they typically have strong verbal skills.

As of the DSM-5, Asperger’s is no longer a standalone diagnosis and is now considered part of Level 1 Autism Spectrum Disorder. However, many people still identify with the term Asperger’s, and it remains widely recognized in education and support communities.

🔗 Learn more about Asperger’s Syndrome →

What does PDD-NOS mean and is it still diagnosed today?

PDD-NOS (Pervasive Developmental Disorder – Not Otherwise Specified) was a former diagnosis for individuals who showed some traits of autism but didn’t meet the full criteria for Autistic Disorder or Asperger’s. It was often used when symptoms were milder or appeared later in development.

Since 2013, PDD-NOS has been replaced by the broader diagnosis of Autism Spectrum Disorder (ASD) in the DSM-5. People previously diagnosed with PDD-NOS are now considered to fall somewhere on the autism spectrum, often at Level 1 or Level 2 depending on support needs.

🔗 Learn more about PDD-NOS →

What is Classic Autism (Autistic Disorder)?

Classic Autism, also called Autistic Disorder, was a diagnosis used before 2013 to describe individuals with significant challenges in communication, social skills, and behavior. Symptoms typically appeared before age 3 and were more intense than those seen in Asperger’s or PDD-NOS.

Today, this form of autism is generally considered Level 2 or Level 3 Autism Spectrum Disorder, depending on how much support the individual needs. While the term “classic autism” is no longer used clinically, it is still referenced in educational and advocacy settings.

🔗 Learn more about Classic Autism →

This page provides general educational content and is not a substitute for professional medical advice. Always consult a licensed provider for diagnosis and treatment.

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Frequently Asked Questions

What are the different levels of autism?

Autism is categorized into three levels based on the support a person needs: Level 1 (mild or high-functioning, needing some support), Level 2 (moderate, requiring substantial support), and Level 3 (severe, requiring very substantial support). These levels help professionals develop personalized treatment plans and support strategies.

What is the difference between classic autism, Asperger's syndrome, and PDD-NOS?

Classic Autism (Autistic Disorder) involves significant language delays and social and behavioral challenges; Asperger's Syndrome involves average to high intelligence and no significant speech delay but difficulty with social skills and sensory sensitivities; and PDD-NOS described people who showed some autism traits but didn't meet the full criteria for the other subtypes. Today all three are recognized as part of ASD.

Is Asperger's syndrome still a diagnosis?

As of the DSM-5, Asperger's is no longer a standalone diagnosis and is now considered part of Level 1 Autism Spectrum Disorder. However, many people still identify with the term, and it remains widely recognized in education and support communities.

What traits are linked to each level of autism?

Level 1 (mild) may include trouble with social cues, inflexible thinking, a preference for routines, and appearing shy or socially awkward. Level 2 (moderate) may include noticeable speech delays, difficulty coping with change, and repetitive behaviors like hand-flapping, while Level 3 (severe) may include nonverbal or limited communication, extreme sensory sensitivities, and frequent meltdowns or shutdowns.

What does it mean if my child has Level 3 autism?

Level 3 autism (requiring very substantial support) involves severe impairments in verbal and nonverbal communication and a strong reliance on caregivers or full-time support. Children at this level may be nonverbal or have limited communication, extreme sensory sensitivities, and frequent meltdowns or shutdowns.