The Five Types of Autism

Autism is a neurodevelopmental condition that affects communication skills, social interaction, and behavior. It varies significantly from one person to another. Although autism has been described using different “types,” these categories were historically used to describe different forms based on symptom severity and the age at which symptoms appear. Today, clinicians commonly use the umbrella term Autism Spectrum Disorder (ASD) to refer to these conditions.

Below are the five commonly referenced types of autism:

  • Classic Autism (Kanner’s Syndrome)
  • Asperger’s Syndrome
  • Rett Syndrome
  • Pervasive Developmental Disorder (PDD / PDD-NOS)
  • Childhood Disintegrative Disorder (CDD) / Heller’s Syndrome

Classic Autism (Kanner’s Syndrome)

Classic autism also known as Kanner’s Syndrome—is a neurodevelopmental disorder that affects an individual’s communication and social interaction skills. It typically appears in early childhood and is characterized by behaviors such as difficulty communicating with others, challenges in social interaction, and restricted, repetitive interests and behaviors.

Kanner’s Syndrome was first identified by Austrian psychiatrist Leo Kanner in 1943, when he described 11 children who showed similar behaviors such as lack of interest in others, delayed language development, and repetitive behaviors. For this reason, it is often considered one of the more challenging forms due to the intensity of symptoms, and research has since contributed to a better understanding of the condition and its underlying causes.

One of the main symptoms of Kanner’s Syndrome is difficulty with social interaction. Individuals may struggle to build relationships, make and maintain friendships, and interpret social cues. This can make it difficult for them to understand nonverbal language, sarcasm, and even tone of voice.

Asperger’s Syndrome

Asperger’s Syndrome is often described as a milder form of autism. Individuals typically have average or above-average intelligence but may experience difficulties with communication and social interaction. Key symptoms include difficulty understanding social cues, limited eye contact, reduced empathy, and intense or obsessive interests in specific topics.

Rett Syndrome

Rett Syndrome is a rare genetic disorder that primarily affects females. Unlike other autism-related conditions, Rett syndrome develops after a period of typical development (usually 6–18 months). It is characterized by loss of speech and motor skills, unusual hand movements, repetitive behaviors such as body rocking, breathing difficulties, and seizures.

Pervasive Developmental Disorder (PDD / PDD-NOS)

Pervasive Developmental Disorder (PDD-NOS) describes individuals who do not fit neatly into a specific category but still show significant symptoms. Symptoms can range from mild to severe and may include social interaction difficulties, communication challenges, and repetitive behavioral patterns. Individuals may have difficulty understanding social cues, maintaining eye contact, making friends, and engaging in typical play activities—so it is sometimes discussed in the context of autism in adults as well.

Childhood Disintegrative Disorder (CDD) / Heller’s Syndrome

Childhood Disintegrative Disorder (CDD)—also known as Heller’s Syndrome—is a rare form of autism seen in children, typically between the ages of 3 and 4. It is marked by a sudden and significant regression in social and language skills. Children with CDD may lose previously acquired skills such as speech, show reduced interest in activities, and experience deterioration in social functioning.

Repetitive behaviors may also appear, such as hand flapping, toe walking, and spinning in circles. It is also noted to affect males more than females.

Children who develop Heller’s Syndrome often begin showing delays in cognitive development and may display signs consistent with Autism Spectrum Disorder. They may become less responsive to social cues and lose interest in interacting with family members or friends.