The differences between the disorders on the autism spectrum

There are several different disorders on the autism spectrum, called ASD’s (Autism Spectrum Disorders.) There is much confusion in terminology these days. Many people have a hard time understanding what the symptom differences are between the disorders. Here is a starter guide to understanding the spectrum – which disorders fall on the spectrum, as well as some conditions that have similar symptoms as ASD’s, but do not fall on the spectrum. 


What is the autism spectrum?

According to Autism Speaks, “autism and autism spectrum disorder (ASD) are both general terms for a group of complex disorders of brain development. These disorders are characterized in varying degrees by difficulties in social interaction, verbal and nonverbal communication and repetitive behaviors.”

Autism Spectrum Disorders

High-Functioning Autism

High-functioning autism isn’t an official medical term, but it is commonly used to talk about someone on the autism spectrum who:

  • Has a difficult time with communication and social interaction
  • Does not make much eye contact or small talk
  • Is organized and likes routine
  • How the person handles work or school – some do well in school, others don’t. Some can hold a job, others find it hard.

Asperger’s Syndrome

Also classified as DSM-5, Asperger’s is part of the ASD spectrum. The symptoms are very similar to high-functioning autism – including:

  • Lack of eye contact
  • Troubles with social skills
  • Lack of emotion

There is an ongoing debate whether high-functioning autism & Asperger’s should be two separate diagnosis as the symptoms are very similar. The primary difference is that a diagnosis of high-functioning autism requires that, early in development, the child had delayed language, where in Asperger’s, the child did not show a significant delay in language development.

Classic Autism

The primary difference between high-functioning autism, Asperger’s and classic autism is IQ. People with high-functioning autism and Asperger’s have IQ’s that are on the normal or even superior level. Usually healthcare providers misdiagnose children at an early age with classic autism rather than Asperger’s. This occurs because the symptoms of Asperger’s are more easily identified at a later age (primarily due to the late onset of complex social skills.)

Pervasive Developmental Disorders

Again, this is another term that is no longer used medically; in 2013 the American Psychiatric Association reclassified PDD’s as ASD’s. Therefore the term “pervasive developmental disorders” before 2013 would now be used to reference someone on the spectrum. 

Conditions similar to ASD’s

Rett Syndrome

Rett Syndrome used to be considered an ASD, however specialists have been able to classify this as a genetic condition (therefore, it is not an ASD.) Rett Syndrome is a neurological condition that mostly affects girls. 

Symptoms include:

  • Slowed growth
  • Trouble with hand movements
  • Problems with coordination and muscular movement
  • Lack of coordination

Other disorders mistaken for autism

Developmental delays, lead poisoning or down syndrome are all conditions that can be mistaken for autism. The symptoms are very similar across the board – slow motor movements, problems with social interaction, and impaired thinking skills.