The “five types of autism” come from an older diagnostic system used before 2013. Under the DSM-IV, clinicians recognized five separate conditions under the umbrella of pervasive developmental disorders: Autistic Disorder, Asperger’s Disorder, PDD-NOS, Rett’s Disorder, and Childhood Disintegrative Disorder. Today, most of these have been merged into a single diagnosis called autism spectrum disorder (ASD), which uses a three-level support system instead. Here’s what each of those original five types looked like and how the diagnosis works now.
The Five Original Types of Autism
From 1994 until 2013, the main diagnostic manual used by clinicians in the United States listed five distinct disorders under pervasive developmental disorders. Each had its own set of criteria, and a child could receive one diagnosis but not another. In practice, the boundaries between several of these conditions were blurry, which eventually led to the system being overhauled.
Autistic Disorder
This was the most severe of the five and what most people pictured when they heard the word “autism.” Children diagnosed with Autistic Disorder typically showed significant difficulties with social interaction, delayed or absent language skills, and repetitive behaviors or intensely narrow interests. Symptoms appeared before age three and affected daily functioning across the board.
Asperger’s Disorder
Asperger’s was often described as “high-functioning” autism, though that label has fallen out of favor. The key distinction was language: children with Asperger’s generally developed speech on time and had age-appropriate language skills. They still struggled with social interaction, reading social cues, and managing restricted interests or repetitive routines. Many had average or above-average intelligence, which sometimes masked the extent of their difficulties.
PDD-NOS (Pervasive Developmental Disorder, Not Otherwise Specified)
PDD-NOS was the catch-all category. It was introduced in 1987 to capture children who had clear social and communication difficulties but didn’t fully meet the criteria for Autistic Disorder or Asperger’s. Sometimes called “atypical autism,” it covered a wide range of presentations. A child might have fewer repetitive behaviors than expected for an Autistic Disorder diagnosis, or their symptoms might have appeared later than age three. Because the criteria were loosely defined, PDD-NOS became one of the most commonly assigned diagnoses in the group, and clinicians often disagreed about where to draw the line.
Rett’s Disorder
Rett’s Disorder (now called Rett syndrome) was included under the autism umbrella because children with the condition often showed social withdrawal and repetitive hand movements that looked similar to autism. However, Rett syndrome has a specific genetic cause: mutations in the MECP2 gene. It almost exclusively affects girls and follows a distinctive pattern where development appears normal for the first six to eighteen months before skills begin to regress. Children lose purposeful hand use and develop characteristic wringing or squeezing hand motions. Because the cause and progression are so different from autism, Rett syndrome was removed from the autism category when the diagnostic system was updated in 2013. It’s now classified as a separate genetic neurological disorder.
Childhood Disintegrative Disorder
This was the rarest of the five. Children with Childhood Disintegrative Disorder developed normally for at least two years, sometimes longer, before dramatically losing skills they had already gained. A child who had been speaking in sentences, playing with peers, and using the toilet independently might lose all of those abilities over a period of weeks or months. The regression was more severe and occurred later than the mild skill loss sometimes seen in Autistic Disorder. Because it was so uncommon, relatively little research existed on it compared to the other subtypes.
Why the Five Types Were Merged
In 2013, the American Psychiatric Association published the DSM-5, which collapsed Autistic Disorder, Asperger’s, PDD-NOS, and Childhood Disintegrative Disorder into one diagnosis: autism spectrum disorder. Rett’s Disorder was removed entirely.
The main reason for the change was reliability. Studies consistently showed that two different clinicians evaluating the same child often assigned different subtypes. A child diagnosed with Asperger’s at one clinic might receive a PDD-NOS diagnosis at another, simply because the boundaries between categories were too vague. The differences between subtypes looked more like points on a continuum than truly separate conditions. A single spectrum diagnosis, the reasoning went, would be more accurate and more consistent.
How Autism Is Classified Now
Instead of five subtypes, the current system uses three support levels that describe how much help a person needs in daily life. These levels apply to two core areas: social communication and restricted or repetitive behaviors.
Level 1, “Requiring Support”: People at this level can speak and function independently in many situations but have noticeable difficulty initiating social interactions. They may respond in unusual ways when others reach out to them or seem less interested in socializing. Repetitive behaviors or fixed interests are present and can get in the way of everyday tasks, but with some support, they manage well. Many people who would have previously received an Asperger’s diagnosis fall into this category.
Level 2, “Requiring Substantial Support”: Social difficulties are more obvious here, even to a casual observer. People at this level have limited ability to start or sustain conversations and may struggle to form relationships even with support in place. Their restricted interests and repetitive behaviors are clearly apparent and interfere with functioning across multiple settings. Interrupting those routines or interests can cause significant distress.
Level 3, “Requiring Very Substantial Support”: This level describes people with severe daily impairment. Verbal communication may be extremely limited. Social interaction is minimal, with very little initiation and only brief responses to others. Fixed rituals and repetitive behaviors dominate daily life and make it very difficult to cope with any change in routine. People at this level need intensive, ongoing support.
These levels aren’t permanent labels. A person’s support needs can shift over time with development, therapy, and changes in their environment. Someone might function at Level 1 in a calm, structured setting but need Level 2 support in a noisy, unpredictable one.
What the Diagnosis Looks Like Today
Current CDC data from 2022 puts autism prevalence at about 1 in 31 children aged eight, a significant increase from earlier estimates. Rates vary widely by region, ranging from roughly 1 in 100 in some areas to more than 1 in 19 in others. Much of that variation reflects differences in screening and access to evaluation rather than true differences in how common autism is.
Alongside the support level, clinicians now note whether a person also has an intellectual disability or a language disorder. This “specifier” system replaced the old subtypes and captures the same range of presentations in a more flexible way. A person might be diagnosed with ASD Level 1 without intellectual impairment and with intact functional language, which roughly maps onto what used to be called Asperger’s. Another person might receive ASD Level 3 with accompanying intellectual disability and limited language, a profile closer to what was once called severe Autistic Disorder.
The international diagnostic system (ICD-11), used in much of the world outside the United States, takes a similar approach. It uses the same single autism spectrum disorder diagnosis with qualifiers for intellectual functioning and language ability.
If you were diagnosed under the old system, that diagnosis doesn’t disappear. Many adults still identify with terms like Asperger’s, and clinicians generally recognize older diagnoses as valid. The shift in terminology reflects updated scientific understanding, not a change in who qualifies for support.