Autism spectrum disorder is the diagnostic label given to a broad category of neurodevelopmental disorders.

These types used to be diagnosed individually by differences and intensity of symptoms:

  • autistic disorder
  • Asperger’s syndrome
  • pervasive developmental disorder not otherwise specified (PDD-NOS)
  • childhood disintegrative disorder

In 2013, the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) revised these classifications. All types of autism are now merged into a single diagnosis of autism spectrum disorder (ASD).

Changes in terminology reflect the newer diagnosis. But the previous terminology isn’t completely phased out in conversation. Some providers may still speak of a diagnosis based on its previous diagnostic label. This overlap can be confusing.

Let’s take a closer look at some of the terms you might hear in relation to autism and how they fit into the changing landscape.

The most obvious symptoms tend to involve communication and interaction with others.

Learning, thinking, and problem-solving abilities may be affected. Intellectually, autistic people can be severely challenged to gifted.

Everybody is different. Some people will have many symptoms and some will have only a few. Signs of autism in a 3 year old or 4 year old may look different from those in a teen or adult.

General signs of autism may include:

  • a child who doesn’t respond to their name
  • avoiding eye contact or no awareness when others are speaking
  • not understanding sharing or taking turns
  • dislike of physical contact unless they initiate
  • not looking at objects shown to them
  • not pointing or responding to pointing
  • no facial expressions or unusual facial expressions
  • repeating words or phrases
  • performing repetitive movements (stimming)
  • difficulty expressing needs
  • inability to play “pretend” games, preferring solo play
  • difficulty adapting to change, or having emotional meltdowns
  • hypersensitivity to sound, smell, taste, sight, or touch
  • a need to organize or rigid behavior
  • delayed speech and language skills, or lack of gesturing
  • losing previously learned skills

In older children and adults, you might also notice:

  • difficulty reading body language, facial expressions, and other social cues
  • not getting sarcasm, teasing, or figures of speech
  • speaking in monotone
  • difficulty forming relationships

When autism was categorized by types, diagnosis was complicated and often stressful for families. The lines between the different types of autism could be blurry.

The single diagnosis of ASD takes the emphasis off categorization and places it on early intervention and accessing crucial services.

If you or your child received a diagnosis before the DSM-5 changes, you may still be using the older terminology. That’s perfectly fine. Your doctor may continue to use those terms if they help.

Asperger’s syndrome

Asperger’s syndrome was on the mild end of the spectrum. People with Asperger’s were often considered high functioning, with normal to above average intelligence.

Signs and symptoms included:

  • impairment in social interaction
  • trouble reading facial expressions, body language, and social cues
  • not understanding irony, metaphor, or humor
  • awkward body language, standing too close, or talking too loudly
  • lack of eye contact
  • repeating the same behaviors and activities

To others, these can be interpreted as signs of rudeness, so forming friendships can be challenging. Other signs included:

  • clumsiness
  • poor handwriting
  • a narrow range of interests or preoccupation with a single interest
  • repetitive behaviors
  • a need for routine and rigid rules
  • easily upset when things don’t go as planned

Pervasive developmental disorder, not otherwise specified (PDD-NOS)

The diagnosis of PDD-NOS was given when a developmental disorder didn’t quite meet the criteria for autism, Asperger’s syndrome, Rett syndrome, or childhood disintegrative disorder.

PDD-NOS fell in the mild to middle part of the spectrum. It has also been called “atypical autism.”

Signs of PDD-NOS might have included:

  • deficits in social behavior
  • uneven skill development
  • poorly developed speech and language
  • difficulty accepting change
  • uncommon responses to taste, sight, sound, smell, or touch
  • repetitive or ritualistic behaviors
  • unusual likes and dislikes

Autistic disorder

Autistic disorder was on the severe end of the spectrum. You’d likely see an array of symptoms early on. These involve:

  • challenges with social interaction
  • communication problems
  • repetitive behaviors

Other signs may include:

  • tantrums or “meltdowns
  • sleeping and eating disturbances

Children on the severe end of the spectrum may prefer playing alone, with little to no interest in others or the outside world. A high level of support is needed for them.

Childhood disintegrative disorder

A child with this disorder met normal developmental milestones for the first few years. After that, there was a rapid decline in acquired skills involving:

  • language and communication
  • social skills, play, and self-care skills
  • motor skills, and bowel and bladder control

Childhood disintegrative disorder fell on the severe end of the spectrum.

The spectrum illustrates a broad range of developmental delays and symptom severity.

ASD includes people who have a few mild autistic traits to those who need help with day-to-day functioning. It represents every intelligence level, as well as varying degrees of communication and social abilities.

The differences between one type and another type can be subtle and difficult to determine. Strict categorization may be less important than accessing needed services.

A diagnosis on the spectrum means you can turn attention to assessing individual needs.

Terms like “mild” or “high functioning” are not official diagnoses. But they can be useful in understanding a general range within the spectrum.

You may also have heard about three “levels” of autism, with level 1 being the mildest and level 3 the most severe. These terms are also not used by doctors today.

High functioning autism

High functioning autism describes “mild” autism, or “level 1” on the spectrum.

Asperger’s syndrome is often described as high functioning autism. Symptoms are present, but the need for support is minimal.

Broad autism phenotype

Broad autism phenotype is a group of slight language and personality traits of autism. Symptoms are mild and may not be clinically significant for diagnosis.

Researchers have noted that this is sometimes seen in relatives of people with an autism diagnosis.

Severe autism

Severe autism is sometimes called “level 3” on the spectrum. People with severe autism require help with day-to-day functioning.

Caregiving, or a high level of support, may be needed indefinitely.

Rett syndrome or Rett disorder has also been called “autism-dementia-ataxia-loss of purposeful hand use syndrome.” But it’s not included on the autism spectrum. It’s a brain disorder caused by genetic mutations.

Classic Rett syndrome affects mostly girls, who develop normally for the first few months. Then, symptoms start to appear involving:

  • language and communication
  • learning
  • coordination

Eventually, affected children start to lose control over their hands. Other symptoms include:

  • repeated hand motions
  • slowed growth or small head size
  • spitting and drooling
  • unusual eye movements, staring, or blinking
  • cold extremities
  • sleep disturbances
  • irritability
  • breathing abnormalities
  • seizures
  • curvature of the spine

If you think your child might have symptoms of autism, speak to their pediatrician or a primary care physician. They can refer you to the appropriate specialist, such as a:

You can also request an evaluation from your state’s public early childhood assistance center. It’s free and you don’t need a doctor’s referral or diagnosis. Your local public school district can also provide assistance.

There’s no medical test to diagnose autism spectrum disorder. A doctor can make the diagnosis with a comprehensive behavior evaluation and developmental screening.

Some people on the spectrum will need a minimum of support services. Others will require a lot. Either way, early intervention is associated with long-term positive effects on people with autism.

The diagnosis of autism spectrum disorder includes a number of conditions that were diagnosed separately prior to 2013. The lines between those conditions weren’t always clear and could be confusing for everyone involved.

The spectrum covers a wide range of symptoms and severity. The evolution to the spectrum and changing terminology should help make things easier to understand.

The spectrum may also help speed up diagnosis and access to services. With early intervention, autistic people can learn skills that can last a lifetime.