Over the years, autism has been defined in different ways within the medical and behavioral health community.

DSM – Diagnosing Autism

Specifically, the DSM (diagnostic and statistical manual of mental disorders), the leading source for diagnosing various mental or behavioral disorders in the United States, has changed the criteria or requirements for obtaining a diagnosis of autism (or autism spectrum disorder) throughout its updated editions of the manual.

These changes are not something specific to the diagnosis of autism as other diagnoses receive modifications from time to time.

To receive a diagnosis of autism or any other disorder, the DSM identifies specific behaviors that a person would need to display in order to qualify as having that particular diagnosis.

Related Article: Understanding Autism: What is Autism Spectrum Disorder?

The DSM, currently on its 5th edition, made some changes to the diagnostic criteria for autism when the manual was updated to the DSM-V from the DSM-IV.

Most significantly, the DSM-V combined four separate diagnoses that were in the DSM-IV into one diagnosis.

  • The DSM-IV identified the following four diagnoses:
    • autistic disorder
    • Asperger syndrome
    • pervasive developmental disorder-not otherwise specified (PDD-NOS)
    • childhood disintegrative disorder
  • The DSM-V combines the four diagnoses above into one diagnosis called:
    • autism spectrum disorder

This change was primarily due to the finding that the four diagnosis in the DSM-IV included similar behavioral characteristics just at different severity levels. This led to the development of the focus on autism as being a spectrum (Wright, 2013).

The diagnosis of autism spectrum disorder is now categorized by a person’s difficulties in the area of social communication and social skills as well as restricted or repetitive behaviors.

A related diagnosis to autism spectrum disorder is known as social communication disorder which identifies people who have difficulties in the area of social communication and social skills but who do not struggle as much with restricted or repetitive behaviors.

Levels of ASD

With the changes in the DSM diagnosis of autism (now known more precisely as autism spectrum disorder), also came the levels of ASD.

The levels of ASD allow for more clarity to be placed on a person’s diagnosis of ASD in terms of where they fit on the spectrum. Basically, the levels of ASD range from mild to severe symptoms.

There are three levels of autism: Level 1, Level 2, and Level 3 (Kandola & Gill, 2019).

The levels are assigned to two of the domains of symptoms of the ASD diagnosis.

The levels help to identify severity of symptoms in the domain of social skills as well as the domain of restrictive or repetitive behaviors.

Level 1 ASD is the least severe. This could be viewed as mild autism.

People who qualify as having Level 1 ASD may struggle in social situations and have some concerns with restrictive or repetitive behaviors but they only require minimal support to help them function in their day to day activities.

People with Level 1 ASD are likely able to communicate verbally. They may be able to have some relationships. However, they may struggle maintaining a conversation and making and keeping friends may not come easily or naturally to them.

People with Level 1 ASD may prefer to stick to established routines and feel uncomfortable with changes or unexpected events. They may want to do certain things in their own way.

Level 2 ASD is the middle-range of autism in terms of severity of symptoms and needs for supports.

People who qualify as having Level 2 ASD need more support than people with Level 1 ASD. They have more difficulty with social skills. Their challenges in social situations may be more noticeable to other people around them as compared to those with Level 1 ASD.

People with Level 2 ASD may or may not communicate verbally. If they do, their conversations may be very short or only on specific topics or they may need extensive support in order to participate in social activities.

The nonverbal behavior of people with Level 2 ASD may be more atypical from the majority of their peers. They may not look at someone who is talking to them. They may not make much eye contact. They may not express emotions through tone of voice or through facial expressions in the same way that most other people do.

People with Level 2 ASD struggle more than those with Level 1 ASD regarding their restrictive or repetitive behaviors. They may have routines or habits that they feel they must do and, if these get interrupted, they become very uncomfortable or upset.

Level 3 ASD is the most severe form of autism spectrum disorder.

People with Level 3 ASD show significant difficulties with social communication and social skills. They also have restrictive or repetitive behaviors that often get in the way of functioning independently and successfully with everyday activities.

Although some individuals with Level 3 ASD can communicate verbally (with words), many individuals with Level 3 ASD do not communicate verbally or may not use many words to communicate.

People with Level 3 ASD often struggle with unexpected events. They may be overly or under sensitive to particular sensory input. They have restrictive or repetitive behaviors such as rocking, echolalia, spinning things, or other behaviors that preoccupy their attention.

People with Level 3 ASD require very substantial support to learn skills important for everyday living.

Understanding the Different Types of ASD

Since the publication of the DSM-V in 2013, autism spectrum disorder has been categorized into three different levels. By identifying a person’s diagnosis of ASD as either Level 1, Level 2, or Level 3, more clarity is placed on the severity of autism and the level of supports that may be needed to help that person live a fulfilling and independent life.

Level 1 ASD refers to mild autism which requires the least amount of support.

Level 2 ASD is the middle level of ASD which typically requires substantial support in certain areas.

Level 3 ASD is the most severe type of ASD which requires very substantial support to help the individual perform activities of daily living that are important to social or behavioral skills.


Kandola, A. 2019. Levels of Autism: Everything You Need to Know. Reviewed by Karen Gill, M.D. Retrieved 11/15/2019 from: https://www.medicalnewstoday.com/articles/325106.php

Wright, J. 2013. DSM-5 Redefines Autism. Retrieved 11/15/2019 from: https://www.spectrumnews.org/opinion/dsm-5-redefines-autism/