Autism Spectrum Disorder: Understanding the Different Types of Autism

Autism spectrum disorder (ASD) is a group of developmental disorders that affect the way someone communicates and behaves. It’s fairly common and affects about 1 of every 44 children. 

Over the last 20 years, research has changed how the medical community thinks about and classifies autism. These changes reflect the growing knowledge about the condition. But they can also make it confusing if you’re trying to understand your or a loved one’s diagnosis. So we’re here to explain the evolution of the diagnosis to help you understand ASD. 

What are the original 5 types of autism? 

The medical community used to categorize autism into five different types. This categorization is now out of date. In 2013, the American Psychiatric Association updated “The Diagnostic and Statistical Manual of Mental Disorders” (DSM-5). This changed the way providers diagnose autism.

But many people are still familiar with the old categories. So let’s first go through these types to better understand the updated approach. 

Historically, experts identified five types of autism:

1. Kanner’s syndrome: Many people know this as “classic” autism. In 1943, Leo Kanner described 11 children who had differences in social interaction. As infants, they did not seem interested in their surroundings and had repetitive behaviors such as arm flapping. He also noted difficulty with change and speech differences, like repeating words or phrases. 

2. Asperger’s syndrome: Hans Asperger described this condition in 1944. He observed how some people have normal language development but still have common differences in the way they interact with other people. He also noted how they often have a deep interest in a single topic.

3. Childhood disintegrative disorder: This is also known as “Heller’s syndrome,” and it was first described in 1908. Children who were diagnosed with this condition had normal development up until 3 or 4 years old. At that age, they then seemed to lose developmental milestones, and they never regained those skills.

4. Rett syndrome: This syndrome is associated with genes on sex chromosomes. It’s more common in babies assigned female at birth. Children with this condition may have normal development at first. But then they have decreased head growth, trouble with walking, and loss of speech milestones. 

5. Pervasive developmental disorder: This diagnosis includes people who had features of autism but did not meet specific criteria in one of the above categories. 

Now, instead of five distinct categories, the above conditions are on a continuous spectrum. The current classification system recognizes this. 

How do experts currently categorize autism spectrum disorder? 

The current classification of autism spectrum disorders is more broad and inclusive. It includes people who were diagnosed with four of the previous categories: Kanner’s syndrome (classic autism), Asperger syndrome, childhood disintegrative disorder, and pervasive developmental disorder. But experts no longer use these names or diagnoses. 

Experts no longer consider Rett syndrome as a part of the autism spectrum. They view it as its own entity, caused by a unique genetic abnormality. 

Now, if someone has signs or symptoms of possible autism spectrum disorder, a medical provider evaluates their symptoms under two main categories (domains):

1. The way they interact and communicate with other people

2. Repetitive behaviors, interests, and activities

Someone is diagnosed with autism spectrum disorder when:

• They meet criteria in the two above categories

• Their symptoms start in early childhood (before age 3)

• Their symptoms affect or limit everyday activities 

Let’s describe these two categories in a little more detail.

1. Social interaction and communication 

This first criteria describes differences in the way someone communicates and interacts with others. Some examples include when someone (often a child):

• Does not make eye contact

• Does not respond to their name by 9 months 

• Does not use hand gestures, like waving or pointing, by 12 to 15 months 

• Struggles to hold conversations

• Behaves in a way that does not seem to match what they’re saying or feeling

• Has a voice tone with a robotic or sing-song quality

2. Repetitive behaviors, interests, and activities 

This second criteria describes differences in movements and interests. It also incorporates sensory differences. These symptoms might include:

• Word or phrase repetition

• Fixation on specific topics or interests

• Difficulty with change in routine, especially if that change is minor or slight

• Increased or decreased sensitivity to things like lights, sounds, or the fit of clothes 

What are the different levels of autism? 

Experts can also separate a diagnosis of ASD into different levels. These levels are based on how severe the symptoms are. In other words, the level depends on how much support an individual needs day to day:

1. Level one requires support. People have challenges interacting with others. They may also have trouble transitioning between activities. With support, these impairments may not be noticeable to others. 

2. Level two requires substantial support. Even with support, social challenges are still apparent. People may also have behaviors that affect their basic daily functions.

3. Level three requires very substantial support. Someone’s social and communication challenges affect all areas of life. People in this category can have very limited social interactions. 

How do you diagnose autism?

Healthcare providers screen all children for autism spectrum disorder during a typical well-child visit. This screening typically takes place when a child is between the ages of 18 and 24 months. If they notice possible signs of ASD, they refer the child to a specialized healthcare team. These providers are experts in diagnosing ASD: 

• Pediatricians 

• Neurologists

• Occupational therapists

• Speech pathologists

• Child psychologists or psychiatrists

Why trust our experts?

Written by:

Jill L. Jaimes, MD

Jill L. Jaimes, MD, is a board-certified pediatric emergency medicine physician with over 20 years of clinical experience. She received her medical degree from Baylor College of Medicine and completed her residency and fellowship training at Texas Children’s Hospital.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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