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The various types of Autism are considered a “spectrum disorder” – an umbrella, with a range of autistic syndromes at varying degree of severities. It can also be depicted, and this is my preferred version while educating parents, as a rainbow where the colors blend and overlap. Each of the distinct color represents a particular category of autism. Yet, the transition from one color to the next on a rainbow is similar to the transition from mild to severe autism.

Autism Spectrum - The Rainbow Effect

Fig 1: Autism Spectrum – The Rainbow Effect

Each of these categories demonstrates varying degrees of difficulties a person faces with social, verbal, communicative and repetitive behaviors. Just as a shade in rainbow overlaps and blends with the next color, so does autism making it harder to determine where one level or type of autism starts and where it terminates.

Key Types of Autism

The Journey from Classical Autism to Autism Spectrum Disorder

Till about the 1970s, the classical autism studies included all shades of ASD bundled under a generic term ‘Autism’.

Today, however, physicians, therapists, and researchers consider each of these five categories while referring to specific autism symptoms:

Classical Interpretation of Autism

classical autism

Fig 2: The Classic view of Autism – so 1970s…

Modern Interpretation of Types of Autism

modern autism spectrum

Fig 3: Autism as interpreted today – A Spectrum of Disorders

“Each type of Autism demonstrates a degree of difficulty that a patient faces with verbal, social and communicative interactions. Just as a shade in rainbow overlaps and blends to the next one, so does the autism spectrum; thus turning it into a challenging exercise for physicians to determine where one range in the spectrum starts and where it ends,” comments Mary Alexa, autism therapy specialist.

Autism Severities per Types

Autism Severities

Support Classification of different Autism Types

Each of the above types of Autism mentioned earlier falls into one of the following categories, based on the level of support they require. For more details on the Autism Levels, please check out our page on Autism Spectrum Disorder DSM 5

Autism Categories

An Insight into the Various Types of Autism

Let us now get a deeper insight into each of the following forms of Autism.

Overlap between Asperger's and PPD NOS - key types of autism

Fig 3: Overlap between Asperger’s and PPD NOS

As mentioned at the beginning of this article, the various types of autism spectrum disorders present a significant overlap with one another. The following 3 characteristics are carefully evaluated to arrive at the right conclusion:

For example, it is extremely hard to discriminate between mild PDD and moderate Asperger’s symptoms as a patient may demonstrate both characteristics in the autism spectrum quotient.


These classify people who fall under the high functioning autism spectrum. They are often intelligent and excel in academics and work life. However, their impairment lies in the lack of social skills. While they develop communication and language skills in the same way as any other developing child, their deficits become more obvious with age as they struggle to keep up with the expectations of their family and extended community circles. Read more about Asperger’s

Pervasive Development Disorder

Pervasive Developmental Disorder – Not Otherwise specified is used to classify people who do not fit into any particular category of Autism. They meet some of the criteria for classical autism, but not necessarily all. Their impairments could range from mild to severe requiring support ranging from anywhere between Level 1 to Level 2. Functioning level is usually moderate to high, barring exceptions where they overlap with other disorder syndromes. Read more about PDD NOS

Childhood Disintegrative Disorder

CDD, also known as Heller’s Syndrome is an interesting one;  typically affecting toddlers and pre-schoolers. In this case, the child grows normally until (at least) the age of 2 and then shows a sudden drop in social, communication and behavioral skills. CDD is often overlooked initially by the parents as they tend to attribute this sudden impairment as a ‘transient and temporary’ phase for their child and would expect it to pass away. Read more about CDD

Rett’s Syndrome

Rett’s syndrome occurs only in girls – the only form of Autism Spectrum Disorder can be diagnosed and medically confirmed. Girls with Rett’s Syndrome suffer from significant communication impairment. Also, one of the common symptoms of Rett’s Syndrome is the girl’s limited ability to use their hands for regular activity. Typically this syndrome deteriorates with the girl’s age, thus requiring more support and time. Read more about Rett’s Syndrome

Classical Autism

Among all the various types of Autism, Classical autism is perhaps the broadest and most predominant form of autism. In technical terms, anyone showing autistic tendencies that satisfy the guidelines laid out by “DSM 5 Autism Spectrum Disorder” is termed Autistic.

The effects of autism in such people may range from mild to very severe. Research has shown that the brain of autistic children has a fair number of electric impulses that any other normal brain of similar age. Read more about Classical Autism

To conclude, even though these are the five main types of Autism, the actual list is far more extensive. It is highly likely that any particular individual can exhibit autistic trends from one or more forms of Autism and therefore may require a varying level of support from medical professionals, therapists and (above all) their families.

Join the discussion 7 Comments

  • X. Bauer says:

    This information is incredibly inaccurate and perpetuates stigma against all autistic people.

  • Maggie says:

    Rett Syndrome hasn’t been recognised as a form of autism in decades and it was officially classified under chromosomal and genetic disorders in the DSM-V in 2015. The only reason it was classified as autism was because there was so little research done on it ‘because it only effected a small number of girls’ and it was the only way medical insurance would cover things for those kids. Doctors would say “yes, there’s something seriously wrong with your daughter but we don’t know what” and because there was no diagnosis, the insurance companies would tell parents they’d have to pay for specialised daycares and wheelchairs and leg braces and home aides and specialists across the country who might have some clue as to how to help their baby by themselves. So those babies were diagnosed as ‘autistic’. Not updating this to educate your readers (who may include parents of Rett babies) is a disservice to them.

    • Maggie, you might have wanted to check the date of the blog post, which clearly shows it was made in 2014. Besides, the writer of this post hasn’t been active since 2019. When you come with information of 2015, it’s kind of obvious why this post doesn’t include it.

      Regardless, if you bash someone for incorrect information, you might want to actually verify your own information first.
      The actual reason why Rett’s syndrome got diagnosed as a pervasive developmental disorder, not autism to begin with, has to do with the fact that Rett syndrome often manifests with autistiform behavior. The onset of Rett syndrome is also nearly identical as the autistic disorder and Asperger’s. And at younger ages, it’s very similar to what is known as regressive autism.
      That doesn’t mean there weren’t major differences. Like people with Rett often become socially engaged again as they grow older, are able to use eye movements to communicate their wishes and their movements problems tend to be much more severe than those seen in autistic people. Rett is also known for involving problems with the autonomic nervous system, which is not the case in autism and Asperger’s.
      However, when the DSM-IV was made, it wasn’t actually even known that Rett syndrome was a genetic disorder, as this discovery was only made in 1999, while the DSM-IV was published back in 1994. Without that knowledge, it is kind of hard not to suppose that Rett syndrome might be a really severe variant of a pervasive developmental disorder.

      Also, what you’re saying makes no sense at all. Having a pervasive developmental disorder and autism were always 2 different things. Only since the DSM-V they have become rather similar due to autism, Asperger’s syndrome, PDD-NOS and Heller’s syndrome all being called autism spectrum disorders these days. However, note both the term “spectrum” and “disorders”, ending with an S, meaning multiple. Even these days there’s still recognition in the diagnosis that there are differences, although the ASD diagnosis has caused a huge amount of stigma for especially those with Heller’s syndrome and those who are normal or high-functioning with the regular form of autism.
      Rett syndrome wasn’t autism ever, it was a pervasive developmental disorder. Also, most people with Rett syndrome nowadays still have an autism spectrum disorder together with their Rett syndrome, so the link is most certainly still there. It’s just more similar to Fragile X syndrome, Klinefelter, Prader Willi and some other condition with autistiform behavior.

  • Durham says:

    You may consider watching this video of a Ted Talk by a woman who has ASD. It really helped me understand “the spectrum” (which I am on) much better. This idea of “higher IQ = lesser impairment” is highly erroneous at best. I believe it’s just a “dumbing down” of the whole concept to make it easier to explain.

    In fact, as she notes, the idea of “the spectrum” as a linear concept is extremely flawed because it makes people with “high-functioning” ASD feel that their impairments shouldn’t cause them as much trouble, when they clearly do. The “higher IQ = lesser autism” concept is also, at worst, very damaging to the view that the general public holds of people on the spectrum.

    Honestly, this is why more people on the spectrum should be involved in research and understanding of the condition. Current definitions amount to a parallel of “mansplaining” in my view, since the people defining the terms really have no real frame of reference. Unfortunately, many people on the spectrum will not be tapped for this since, regardless of their actual intelligence (and like me), they likely will not complete any higher education (if indeed they even graduate high school, which I did not).

    A minor aside: There is some pretty rigorous debate over whether or not IQ can even be accurately measured in people with ASD, which I fully understand having been tested many times with widely varying results. I believe this is due to comprehension of the tests themselves more than ability or inability to take them, but that’s just my own unsupported opinion.

    • Patrick says:

      I don’t think they’re claiming that high IQ is equivalent to less impairment, just that those two things seem to correlate.

  • Angela Bullard says:

    I know a specialist in Perth Western Australia AUSTRALIA who treats drug addictions and has a type of autism but was told by a patient that it had a big long name possibly very long (an acronym) and can’t think what it could be?
    Can you please help me?

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