Is There More Than One Autism Spectrum Disorder?

Many Different Autisms; One Autism Spectrum

Autism is a "spectrum disorder," meaning that people with autism may have a wide range of mild, moderate, or severe symptoms. But do all people with an autism spectrum diagnosis have the same disorder, no matter what their symptoms?

How Autism Diagnoses Have Changed in Recent Years

From 1994 to May 2013, the autism spectrum was represented by five autism spectrum diagnoses in the fourth version of the official Diagnostic Manual. They included Asperger syndrome, Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS), Autistic Disorder, Childhood Disintegrative Syndrome, and Rett Syndrome.

Unfortunately, these diagnoses were confusing. Not only were they difficult to define, but different practitioners selected different diagnoses for the same patients. To clarify their diagnoses, practitioners (as well as teachers and therapists) used terms like "severe autism," "mild autism," and "high functioning autism." These terms, however, aren't true diagnoses at all; they're just descriptions. And while they were intended to help parents and teachers better understand a child's status on the autism spectrum, each practitioner had their own idea of what "mild" or "severe" might look like.

How We Think About Autism Today

In 2013, the fifth version of the Diagnostic Manual was published. In the DSM-5, there is just one "autism spectrum disorder." Everyone with an autism diagnosis, no matter what his or her symptoms, is now lumped under that single diagnosis. Three levels of autism, along with descriptors such as "nonverbal" are intended to make diagnosis easier and clearer.

But that doesn't mean we've stopped using the older or informal terms, some of which are a bit clearer than Autism Spectrum Disorder Level II. In fact, even doctors and other practitioners are likely to use terms like Asperger Syndrome while using the new autism spectrum code for billing purposes.

Welcome to the complex world of many autisms.

What Is the Autism Spectrum?

Rainbow. Getty Images

The "autism spectrum" describes a set of developmental delays and disorders which affect social and communication skills and, to a greater or lesser degree, motor and language skills. It is such a broad diagnosis that it can include people with high IQ's and mental retardation. People with autism can be chatty or silent, affectionate or cold, methodical or disorganized.

Until May 2013, official diagnoses within the autism spectrum included autistic disorder, pervasive developmental disorder-not otherwise specified (PDD-NOS), Asperger syndrome, Childhood Disintegrative Disorder, and Rett Syndrome. Today, there is just one Autism Spectrum Disorder, with three levels of severity -- but many therapists, clinicians, parents, and organizations continue to use terms like PDD-NOS and Asperger syndrome.

What Are Pervasive Developmental Disorders?

Kids playing together with telephone cans
KidStock/Getty Images

"Pervasive Developmental Disorder" is a formal term that, between 1994 and 2013, meant exactly the same thing as "autism spectrum disorder." If your child was diagnosed before 2013 you may have heard this term from an evaluator or doctor, but it is not longer in general use.

What Is Asperger Syndrome?

Cute little boy sitting outdoors, wearing crown, looking up at the sky.
Adriana Varela Photography/Moment/Getty

Asperger syndrome describes individuals at the highest-functioning end of the autism spectrum. The term -- and the diagnosis -- was removed from the diagnostic manual in 2013, but virtually everyone in the autism community continues to use it because of its usefulness in describing a very specific group of people. People with Asperger syndrome generally develop spoken language in the same way as typically developing children, but have a tough time with social communication. These difficulties that become more obvious as they get older and social expectations rise.; Because people with Asperger syndrome are often very intelligent - but "quirky" - the disorder is sometimes nicknamed "geek syndrome" or "little professor syndrome."

What Is Mild Autism?

Child Doing Jigsaw Puzzle
Getty Images

The term "mild autism" is not an official diagnosis. It's simply a more descriptive term than "Asperger syndrome" or "autism." Generally speaking, when people use the term mild autism they are referring to individuals whose symptoms fit an autism spectrum diagnosis, but who has strong verbal skills and few behavioral issues. Those individuals may, however, have significant problems with social communication. They may also have problems coping with too much sensory input (loud noise, bright lights, etc.).

What Is High Functioning Autism?

Child smiling and looking up at the sky
Thomas Barwick/Taxi/Getty Images

Like "mild" autism, high functioning autism (sometimes shortened to HFA) is a made-up term that's become more and more commonly used. At one point (before 2013), the term was used to distinguish "autism" from "Asperger syndrome." The official distinction made by practitioners before 2013 was that people with HFA had or have speech delays while people with Asperger Syndrome have normal speech development. Of course, these days there IS no Asperger syndrome... making the distinction moot.

What Is PDD-NOS?

Desperately unhappy 7 year old boy looks down

"Pervasive Developmental Disorder Not Otherwise Specified" is a mouthful of words that, until 2013, were used to describe individuals who didn't fully fit the criteria for other specific diagnoses but are nevertheless autistic. Because there is no easy way to define the symptoms of PDD-NOS, which may range from very mild to very severe, the diagnostic category no longer exists, though a new diagnosis, Social Communication Disorder, may become a similar "catchall" category. 

What Is Severe Autism?

screaming boy
Getty Images

Severe autism is not an official diagnosis; instead, it is a descriptive term along with profound autism, low functioning autism, and classic autism. People with "severe autism" are often non-verbal and intellectually disabled, and may have very challenging behaviors.

What Is Rett Syndrome?

little girl anxious near toilet
Getty Images

Rett syndrome is a genetic disorder that affects only girls. It is the only one of the former autism spectrum disorders that can be diagnosed medically (so far) -- and as of May 2013, it is no longer included in the Autism Spectrum. Girls with Rett syndrome develop severe symptoms including the hallmark social communication challenges of autism. In addition, Rett syndrome can profoundly impair girls' ability to use their hands usefully.

What Is the Broad Autism Phenotype?

Portrait of woman crying
Compassionate Eye Foundation/David Oxberry/OJO Images Ltd/Getty Images

The broad autism phenotype includes those people with the merest touch of autism. This is sometimes described as having "shadow symptoms." Such mild symptoms, which are recognizable but which do not impair daily functioning, are common among family members of people with full-blown autism. Is this really autism? Or just a personality type? As with many issues related to autism, it depends on who you ask.

Autism Terms Aren't Always Helpful

While some autism-related terms are descriptive, they're not always terribly helpful. That's because each and every individual on the autism spectrum is unique. Even if you think you know what a term means, it's always important to learn more about a particular individual's strengths and challenges.