High-functioning autism (HFA) was historically an autism classification where a person exhibits no intellectual disability, but may experience difficulty in communication, emotion recognition, expression, and social interaction.
HFA has never been included in either the American Psychiatric Association's Diagnostic and Statistical Manual (DSM) or the World Health Organization's International Classification of Diseases (ICD), the two major classification and diagnostic guidelines for psychiatric conditions.
Characterization
High-functioning autism is characterized by features similar to those of Asperger syndrome. The defining characteristic recognized by psychologists is a significant delay in the development of early speech and language skills, before the age of three years. The diagnostic criteria of Asperger syndrome exclude a general language delay.
Further differences in features of people with high-functioning autism from those with Asperger syndrome include the following: Lower verbal reasoning ability Better visual/spatial skills (Being uniquely artistically talented) Less deviating locomotion (e.g. clumsiness) Problems functioning independently Curiosity and interest for many different things Not as good at empathizing with other people Male to female ratio (4:1) much smaller
Comorbidities
Individuals with autism spectrum disorders, including high-functioning autism, risk developing symptoms of anxiety. While anxiety is one of the most commonly occurring mental health symptoms, children and adolescents with high functioning autism are at an even greater risk of developing symptoms.
There are other comorbidities, the presence of one or more disorders in addition to the primary disorder, associated with high-functioning autism. Some of these include bipolar disorder and obsessive–compulsive disorder (OCD). In particular the link between HFA and OCD, has been studied; both have abnormalities associated with serotonin.
Observable comorbidities associated with HFA include ADHD and Tourette syndrome. HFA does not cause, nor include, intellectual disabilities. This characteristic distinguishes HFA from low-functioning autism; between 40 and 55% of individuals with autism also have an intellectual disability.
Behavior
An association between HFA and criminal behavior is not completely characterized. Several studies have shown that the features associated with HFA may increase the probability of engaging in criminal behavior. While there is still a great deal of research that needs to be done in this area, recent studies on the correlation between HFA and criminal actions suggest that there is a need to understand the attributes of HFA that may lead to violent behavior. There have been several case studies that link the lack of empathy and social naïveté associated with HFA to criminal actions.
There is still a need for more research on the link between HFA and crimes, because many other studies point out that most people with ASD are more likely to be victims and less likely to commit crimes than the general population. But there are also small-subgroups of people with autism that commit crimes because they lack understanding of the laws they have broken. Misunderstandings are especially common regarding autism and sex offenses, since many people with autism do not receive sex education.
Cause
Although little is known about the biological basis of autism, studies have revealed structural abnormalities in specific brain regions. Regions identified in the "social" brain include the amygdala, superior temporal sulcus, fusiform gyrus area and orbitofrontal cortex. Further abnormalities have been observed in the caudate nucleus, believed to be involved in restrictive behaviors, as well as in a significant increase in the amount of cortical grey matter and atypical connectivity between brain regions.
Diagnosis and IQ
HFA is not a recognised diagnosis by the American Psychiatric Association or the World Health Organization. HFA is often, however, used in clinical settings to describe a set of symptoms related to an autism spectrum disorder whereby they exhibit standard autism indicators although have an intelligence quotient (IQ) of 70 or greater.
For modern IQ tests, the raw score is transformed to a normal distribution with mean 100 and standard deviation 15. This results in approximately two-thirds of the population scoring between IQ 85 and IQ 115 and about 2.5 percent each above 130 and below 70.