Categorical and dimensional structure of autism spectrum disorders: the nosologic validity of Asperger Syndrome.

There is an ongoing debate whether a differentiation of autistic subtypes, especially between Asperger Syndrome (AS) and high-functioning-autism (HFA) is possible and if so, whether it is a categorical or dimensional one. The aim of this study was to examine the possible clustering of responses in different symptom domains without making any assumption concerning diagnostic appreciation. About 140 children and adolescents, incorporating 52 with a diagnosis of AS, 44 with HFA, 8 with atypical autism and 36 with other diagnoses, were examined. Our study does not support the thesis that autistic disorders are discrete phenotypes. On the contrary, it provides evidence that e.g. AS and autism are not qualitatively distinct disorders, but rather different quantitative manifestations of the same disorder.