[14][15][16][17] HFA has never been included in either the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM) or the World Health Organization's International Classification of Diseases (ICD), the two major classification and diagnostic guidelines for psychiatric conditions.
The defining characteristic recognized by psychologists was a significant delay in the development of early speech and language skills, before the age of three years.
[19] Other differences noted in features of high-functioning autism and Asperger syndrome included the following:[12][20][21][22] HFA is not a recognised diagnosis by the American Psychiatric Association or the World Health Organization.
HFA was, however, previously used in clinical settings to describe cases of autism spectrum disorder where indicators suggested an intelligence quotient (IQ) of 70 or greater.
[26] Some case studies have linked the lack of empathy and social naïveté associated with HFA to criminal actions.