Five different Autism Spectrum

Older classifications of autism are no longer used, but they can help us understand the current spectrum diagnosis. They include five major types: Asperger’s Syndrome, Pervasive Developmental Disorder (PDD)—Not Otherwise Specified (NOS), Childhood Disintegrative Disorder (CDD), Rett Syndrome (RTT), and Autistic Disorder. The range of abilities across the ASD spectrum is vast. While one child with ASD may be nonverbal, another may be a highly skilled communicator. One child with ASD may have average to above-average intelligence, while another may have significant cognitive challenges.

1. Kanner’s syndrome

Kanner’s syndrome is an outdated term for autism. It was originally identified in children who displayed social impairments and repetitive behaviours. Autism is now known to be a broader spectrum that affects people of all ages. We now know it is more common than previously thought, with 1 in 44 children identified with autism spectrum disorder.

2. Asperger’s Syndrome

Asperger’s Syndrome was once a separate diagnosis from autism but was later reclassified as a subtype of Autism Spectrum Disorder. Many people who have been diagnosed with Asperger’s still feel a connection to that term and prefer it to the autism diagnosis. While Asperger’s and autism share traits, they also have unique differences, and identifying those differences is helpful in helping loved ones lead better lives.

3. Rett Syndrome

Rett Syndrome is a condition that was once thought to be a type of autism. Now, Rett Syndrome is recognised as a distinct genetic disorder that primarily affects girls. Rett Syndrome was removed from the autism diagnosis because it has key differences from autism, like primarily presenting in girls and including specific physical symptoms. It is a genetic disorder caused by a mutation of the MECP2 gene. While it is rarely passed down in families, it can be linked to other gene mutations as well. There are four stages to Rett Syndrome, but the progression of symptoms is different for every person with the condition.

4. Childhood Disintegrative Disorder (CDD)

Childhood Disintegrative Disorder was once thought to be a severe form of autism but has since been absorbed into the broader category of Autism Spectrum Disorder. CDD is a rare disorder that is defined by the loss of previously learned skills, like language, in typically developing children. Children with CDD may display signs of autism, like repetitive behaviours and loss of speech, as well as an extreme loss of any skills learned before the regression began. It is considered a very rare condition.

5. Pervasive Development Disorder Not Otherwise Specified (PDD-NOS)

Before the DSM-5, there were three main types of autism that included PDD-NOS. The primary difference between PDD-NOS and other types of autism was that it did not meet all of the criteria for the former diagnosis of autism. PDD-NOS was the diagnosis for children who displayed developmental delays and difficulties but did not meet the standards for a diagnosis of autism.

When the DSM-5 was published, PDD-NOS and two other diagnoses were all removed to help provide a more uniform standard of diagnosis for ASD and to ensure that loved ones with the condition had access to the resources.