Types of Autism Spectrum Disorder: The Current Classification, Explained

Search for the types of autism and you will find lists: classic autism, Asperger's syndrome, PDD-NOS, Rett syndrome, childhood disintegrative disorder. Those lists describe a system that clinicians in the United States stopped using in 2013.

Since then there has been one diagnosis. A child evaluated today in New Jersey, North Carolina, or Colorado either meets criteria for autism spectrum disorder (ASD) or does not. That single label covers an enormous range of presentations, which is what people are gesturing at when they describe someone as being on the spectrum. What varies between children is not the diagnosis. It is how much support the evaluation says the child needs, and in which areas.

This article covers what replaced the old categories, how the three support levels work, which retired terms you will still hear from relatives and school staff, and which conditions are genuinely separate diagnoses that get mistaken for autism. These are the same questions our clinical team works through with families during intake.

One Diagnosis Replaced the Old Types of Autism

Before 2013, the Diagnostic and Statistical Manual of Mental Disorders (DSM), the reference book U.S. clinicians use to make psychiatric and developmental diagnoses, listed five conditions under a heading called pervasive developmental disorders. Those were autistic disorder, Asperger's disorder, PDD-NOS, childhood disintegrative disorder, and Rett syndrome.

The fifth edition dissolved that heading. Peer-reviewed reviews of the change describe autistic disorder, Asperger's, childhood disintegrative disorder, and PDD-NOS as having been collapsed into one category: autism spectrum disorder. Rett syndrome was handled differently and is covered further down.

The reason for the merge was practical. Research found the old subtypes were not applied consistently between clinics, so the same child could receive different labels depending on who did the evaluation.

This is not a small administrative population. CDC surveillance across 16 sites found that about 1 in 31 children aged 8 had been identified with ASD in 2022, up from 1 in 36 two years earlier. Consistent criteria matter at that scale.

Retired Labels You Will Still Hear

Old terms have a long afterlife in families, schools, and paperwork. A few worth recognizing:

Asperger's syndrome. Removed as a separate diagnosis in 2013. Many adults diagnosed under the old system continue to use the term for themselves, and that is a reasonable personal choice. It is no longer something a clinician can assign.

PDD-NOS. A catch-all for children with clear social and communication differences who did not meet the full criteria for autistic disorder.

Classic autism, or autistic disorder. The narrowest of the old categories.

High-functioning and low-functioning. These were never diagnostic terms. They compress a child into a single ranking and tend to obscure the actual picture, which is usually uneven: strong reading with limited speech, or fluent speech with significant difficulty regulating emotion.

Existing diagnoses were not invalidated by the change. The DSM-5 states that anyone with a well-established diagnosis of autistic disorder, Asperger's disorder, or PDD-NOS should be given the diagnosis of autism spectrum disorder. Families do not need to seek re-evaluation solely because the manual was updated.

What the DSM-5 Autism Criteria Actually RequireThe DSM-5 autism criteria are built on two symptom domains, and a child must show difficulties in both. Understanding the structure helps when you read an evaluation report, because reports are usually organized the same way.

The first domain is social communication and social interaction. A child must show persistent differences in all three areas:

• Social and emotional back-and-forth, such as starting conversations or sharing interests
• Nonverbal communication, such as eye contact, gestures, and facial expression
• Developing, keeping, and understanding relationships, including imaginative play with peers

The second domain is restricted and repetitive patterns of behavior, interests, or activities. Here a child must show at least two of four:

• Repetitive movements, speech, or use of objects, such as lining up toys or echolalia (repeating words or phrases heard elsewhere)
• Insistence on sameness and distress at small changes
• Highly fixated interests that are unusual in intensity or focus
• Over- or under-reaction to sensory input, such as covering ears at certain sounds or seeking out specific textures

Three more conditions apply. Symptoms must be present in the early developmental period, though they may not become obvious until social demands increase. They must cause meaningful difficulty in daily life. And they must not be better explained by intellectual disability or global developmental delay, which is why a thorough evaluation looks at cognitive testing alongside behavior. Reviewing early developmental history is part of that process.

Because autism is defined by observed behavior rather than by a lab result, being able to see the behaviors described above is genuinely useful.

Kennedy Krieger Institute's nine-minute tutorial, developed by autism researcher Dr. Rebecca Landa, compares one-year-olds who show early signs with one-year-olds who do not, with voice-over explaining what to look for as it happens on screen.

The Three Support Levels, and What They Do Not Mean

Rather than sorting children into types, the DSM-5 assigns a severity specifier. The three levels of autism are worded as statements about support, not about the child:

• Level 1: Requiring support. Difficulty starting social interactions and responding to others in expected ways. Inflexibility interferes with functioning in one or more settings.
• Level 2: Requiring substantial support. Social communication differences are apparent even with supports in place. Repetitive behaviors and distress at change are frequent enough that others notice.
• Level 3: Requiring very substantial support. Significant limits in verbal and nonverbal communication, very limited initiation of interaction, and marked difficulty coping with change.

Three points about these levels are routinely misunderstood.

First, the level is not one number. Severity is rated separately for social communication and for restricted and repetitive behavior, so a child can be Level 1 in one domain and Level 2 in the other. Descriptions from clinical research centers set out what each level covers in each domain.

Second, the level is not an IQ score. The DSM-5 records intellectual and language ability as separate specifiers, which is why a report may read "autism spectrum disorder, Level 2, without accompanying intellectual impairment."

Third, the level is a snapshot, not a permanent assignment. Support needs shift with age, environment, and intervention. A rating made at age three describes a three-year-old.

Conditions Sometimes Confused With Autism

These are separate diagnoses. Some appeared on the old types-of-autism lists and no longer belong there. Others overlap enough in early presentation that a careful evaluation has to rule them in or out.

The distinction is not academic. A diagnosis determines which specialists a child is referred to, which services insurance will authorize, and which medical monitoring is appropriate. A genetic condition and a behaviorally defined developmental condition call for different follow-up, even when the day-to-day support looks similar.

Is Rett Syndrome a Type of Autism?

No. Rett syndrome is a genetic condition and has not been part of the autism spectrum since 2013. Between 90% and 95% of girls with Rett syndrome have a mutation in the MECP2 gene on the X chromosome, which was identified by NICHD-supported researchers in 1999.

Because the cause is known and testable, Rett syndrome was moved out of the autism category when the DSM-5 was published. Autism is still defined by observed behavior; Rett syndrome can be confirmed by a blood test alongside clinical criteria.

The confusion is understandable. NICHD notes that Rett syndrome is sometimes misdiagnosed as regressive autism or cerebral palsy, because the pattern of typical development followed by loss of skills looks similar from the outside. The distinguishing features include partial or complete loss of purposeful hand skills and slowed head growth between three months and four years of age.

Childhood Disintegrative Disorder

Also called Heller's syndrome. This one is a retired label rather than a separate condition. It described a child who developed typically for at least two years and then lost language, social, and motor skills. When the DSM-5 was published, childhood disintegrative disorder was folded into autism spectrum disorder rather than removed from it.

A child today with that history is evaluated for ASD, usually with substantial support needs recorded, plus a medical workup to check for other causes of regression. The pattern still matters clinically. It just does not carry its own diagnostic code.

Social (Pragmatic) Communication Disorder

A DSM-5 diagnosis for children who have marked difficulty with the social use of language but do not show the restricted and repetitive behaviors autism requires. The DSM-5 directs clinicians toward this evaluation when a child meets part of the autism criteria but not the whole.

Intellectual Disability and Global Developmental Delay

Both can produce delayed speech and limited social engagement. The criteria specifically require that autism symptoms not be better explained by these conditions, though they frequently co-occur with autism and can be diagnosed alongside it.

ADHD

Attention differences, impulsivity, and difficulty with transitions appear in both. The two also co-occur often enough that evaluations increasingly screen for both. We cover the overlap between them in more detail separately.

What This Means for Therapy Planning

A support level is a starting point for a conversation, not a treatment plan. Two children rated Level 2 can need almost nothing in common: one may need communication as the priority, another may need help with daily routines and self-regulation.

That is why assessment comes before programming. A BCBA (Board Certified Behavior Analyst, the clinician who designs and supervises ABA programs) builds goals from direct observation and family priorities, not from the number on the diagnostic report.

If you are reviewing an evaluation now, three questions tend to be more useful than the level itself. Which specific skills did the evaluator observe, and which did they not get to see. What did the report recommend as an immediate priority. And which co-occurring conditions, if any, were screened for. Answers to those questions carry more planning value than the severity specifier does. That sequence shapes how programs are built here, and the range of formats available, including in-home, school-based, and parent training, is described on our ABA services page.

Where you live shapes what comes next as much as the diagnosis does. Evaluation wait times, insurance requirements, and early intervention eligibility differ by state. Families in New Jersey, North Carolina, and Colorado can find state-specific information on those pages, including how services are typically funded and what documentation is usually requested.

If You Are Still Sorting Through This

Reading about diagnostic categories can leave you with more questions than answers, particularly if your child's report used terms nobody explained. There is no pressure here to switch providers or to make a decision on any timeline.

If it would help to talk through what a support level means for your child, or what an evaluation report is actually saying, you can send us a note. We will answer questions about the diagnosis itself even if you never become a client. If the right next step for your family is staying with your current provider, we will say so.

Frequently Asked Questions

Sources:

• https://www.cdc.gov/autism/hcp/diagnosis/index.html
• https://www.psychiatry.org/File%20Library/Psychiatrists/Practice/DSM/APA_DSM-5-Autism-Spectrum-Disorder.pdf
• https://pmc.ncbi.nlm.nih.gov/articles/PMC4929984/
• https://pmc.ncbi.nlm.nih.gov/articles/PMC3635864/
• https://www.nichd.nih.gov/health/topics/rett/conditioninfo/causes
• https://www.nichd.nih.gov/health/topics/rett/conditioninfo/diagnosed
• https://www.cdc.gov/mmwr/volumes/74/ss/ss7402a1.htm
• https://www.research.chop.edu/car-autism-roadmap/diagnostic-criteria-for-autism-spectrum-disorder-in-the-dsm-5