Autism is a brain disorder in which communication and interaction with others is difficult. The symptoms of autism may range from total lack of communication with others to difficulty in understanding others' feelings. Because of the range of symptoms, this condition is now called autism spectrum disorder (ASD).
High-functioning autism (HFA) is a term applied to people with autism who are deemed to be cognitively "higher functioning" (with an IQ of greater than 70) than other people with autism. Individuals with HFA or Asperger syndrome may exhibit deficits in areas of communication, emotion recognition and expression, and social interaction. HFA is not a recognized diagnosis in the DSM-5 or the ICD-10. The amount of overlap between HFA and Asperger syndrome is disputed, however, usually children with HFA have language delays early on like other children with autism. Children with Asperger's, though, don’t show classic language delays until they have enough spoken language to assess language difficulties.
High-functioning autism (HFA) is an informal term applied to autistic people who are deemed to be "higher functioning" than other autistic people, by one or more metrics. There is no consensus as to the definition. HFA is not yet a recognized diagnosis in the DSM-IV-TR or the ICD-10.
A person with high-functioning autism usually has average or above average intelligence. The differences from other forms of autism have led many psychiatrists to consider high-functioning autism as similar to or the same as Asperger's syndrome. However, the amount of overlap between HFA and Asperger syndrome is disputed. Some researchers argue that the two are distinct diagnostic entities, others argue that they are indistinguishable.
Though High functioning autism is not an official diagnostic term, it may be used as such. It tends to describe people who have many or all of the symptoms of autism but did not develop language typically.
Generally speaking, doctors prefer to group people with autistic symptoms into discrete diagnostic categories. Rett syndrome and Fragile X syndrome are relatively clearcut disorders, and thus are likely to be correctly diagnosed. Classic autism is also fairly clearcut: Children with classic autism are usually non-verbal, un-engaged, and unable to perform well on standard diagnostic tests.
Unlike people with other forms of autism, people with high-functioning autism or Asperger's syndrome want to be involved with others. They simply don't know how to go about it. They may not be able to understand others' emotions. They may not read facial expressions or body language well. As a result, they may be teased and often feel like social outcasts. The unwanted social isolation can lead to anxiety and depression.
Children with classic autism are usually non-verbal, un-engaged, and unable to perform well on standard diagnostic tests; however people with high functioning still also demonstrate clearly autistic behaviors. Examples can include, depending upon their age: use of meaningful language, reading, writing, doing mathematics, showing affection, completing daily tasks; but can't hold eye contact, maintain a conversation, engage in play, pick up on social cues, etc. What is the correct diagnosis for such a child? Is it Pervasive Developmental Not Otherwise Specified" (PDD-NOS)Asperger syndrome? High functioning autism
Often understood to mean the same thing as "high functioning autistic," it really incorporates individuals at all function levels whose symptoms don't fully correlate with classic autism. So a PDD-NOS diagnosis may provide some information to parents and teachers but cannot guide treatment.
One useful explanation of the difference between Asperger syndrome and high functioning autism comes from the National Autism Society in the UK. Here's what it says: