The term 'autism' was first used by the psychiatrist Kanner in 1943. Over the years the terms describing autism have developed/changed as more knowledge has been gained. 'Autistic Spectrum Disorder' refers to the whole range of 'autistic style' symptoms with their varying degrees and differing ranges of symptoms and is used to describe those mildly affected through to those with the most profound disability. For example, High Functioning Autism and Asperger Syndrome are both subgroups of the Autistic Spectrum Disorder. The condition is caused by subtle differences in the physical construction of the brain; it isn't a psychological condition.
Autistic Spectrum Disorder is a life-long developmental disorder usually characterised by the so called triad of impairments,
These characteristics vary with both severity and age. However there is always the potential for improvements, especially for those with higher levels of ability.