Why Is 'High Functioning Autism' So Hard to Define?

Terms Like 'High Functioning Autism' Can Be Confusing

Kids in art class
Hero Images/Getty Images

In a very general way, "high functioning autism" means "a person with relatively mild symptoms which, despite their mildness, are significant enough to merit an autism spectrum diagnosis." 

But there is no formal diagnosis called "high-functioning autism," and no agreed upon definition of "high functioning." Add to this the fact that many people with autism may be bright, accomplished, and yet have severe symptoms (such as anxiety and sensory dysfunction) that significantly impact their daily functioning.

As you can see, the term is hard to pin down.

Isn't High Functioning Autism the Same as Asperger Syndrome?

Until 2013, many people who might be said to have high functioning autism were diagnosed with either Asperger syndrome or PDD-NOS (Pervasive Developmental Disorder Not Otherwise Specified)

  • Asperger syndrome was a distinct diagnosis which described a person of average or higher-than-average intelligence and age appropriate language skills who also had significant social and communication challenges.
  • PDD-NOS was a catch-all diagnosis. Often understood to mean the same thing as "high functioning autistic," it really incorporated individuals at all functional levels whose symptoms didn't fully correlate with classic autism.

As of 2013, with the publication of the DSM-5, neither PDD-NOS nor Asperger syndrome are official diagnostic categories in the United States. 

Is 'Level 1' Autism the Same as 'High Functioning Autism?'

With the DSM-5, instead of separate diagnoses, there is just one big group of people diagnosed with Autism Spectrum Disorder.

 But people with autism are still very different from one another.  So, to clarify these differences, the DSM-5 also includes functional levels. People who are bright and verbal (and thus, theoretically at least, in need of less support) are generally given the diagnosis of Level 1 Autism Spectrum Disorder.

But what does a person with Level 1 Autism Spectrum Disorder look like? The answer is as diverse as the people who have the diagnosis. For example:

  • They can use age-appropriate language, read, write, do math, show affection, complete daily tasks—but can't hold eye contact, maintain a conversation, engage in play, or pick up on social cues.  
  • They have significant speech and language delays but are able to take part in an inclusive academic program because their age-appropriate academic skills.  
  • They have relatively mild speech and social delays but have severe sensory issues which make it impossible for them to take part in an inclusive academic program. 
  • They have severe anxiety, learning disabilities, and sensory challenges—but have age-appropriate speech and extraordinary abilities in music, math, and engineering.  

In short, the possible combinations of strengths and challenges are almost endless. This means that the concept of "Level 1" autism is also pretty tricky. Apparently, the people who developed the idea of "Levels of Support" were thinking in a very general way—that is, people with Level 3 autism need 24/7 skilled support, while people with Level 1 autism don't. 

How Much Support Does a 'High Functioning' Individual Need?

While few people with "high functioning" autism need help with toileting or basic hygiene, they may very well need a good deal of support in other settings.

 For example, a very bright individual with severe sensory issues, anxiety, and perseveration might actually have a more difficult time in the workplace than a less intelligent individual with less anxiety and fewer sensory issues.

What's more, a "lower functioning" individual might spend most of their day in a supported setting where the possibility of dangerous interactions is almost zero. Meanwhile, the individual with "high functioning" autism may need to navigate a world of complex and hazardous situations. Who needs more support under those circumstances?

No Easy Answers

Autism is a puzzle—not because individuals with autism are so puzzling, but because the ever-changing definitions of autism mean we cannot come to a final conclusion.

And not only are the definitions changing, but so are the social expectations that make high functioning autism so challenging. In the past, for example, face to face communication was the key to personal success; today, many people with social challenges are more than capable of interacting with others online, making friends through social media, and even holding down a job at a distance. Some businesses are hiring high functioning autistic people because of their unique abilities, while others cannot imagine hiring a person with compromised social skills.

If this leaves you feeling that the definition of high functioning autism is clear as mud, you're not alone! At least now, however, you understand why the term is so tough to nail down—and you know you're in good company.


Attwood, Tony. The Complete Guide to Asperger Syndrome. Jessica Kingsley Press: 2007.

How are Asperger Syndrome and High Functioning Autism Different? Autism Speaks. 2017. https://www.autismspeaks.org/family-services/tool-kits/asperger-syndrome-and-high-functioning-autism-tool-kit/how-are-and-hfa-dif

Koyama T, Tachimori H, Osada H, Takeda T, Kurita H. "Cognitive and symptom profiles in Asperger's syndrome and high-functioning autism." Psychiatry Clin Neurosci. 2007 Feb;61(1):99-104.

Seung HK. "Linguistic characteristics of individuals with high functioning autism and Asperger syndrome." Clin Linguist Phon. 2007 Apr;21(4):247-59.

Continue Reading