Measuring autism spectrum disorder: associated features and diagnostic criteria

Abstract

The overall aim of this thesis is to use the distinctive “spectrum” approach uniquely offered by the Diagnostic Interview for Social and Communication Disorders (DISCO) to explore the different descriptions of Autism Spectrum Disorder across four parts of the thesis. Part 1 introduces the concept of an “autism spectrum” and evaluates how this is continually developing. In Part 2, the focus is on the associated behaviours of ASD, that is, the behaviours not used to make a diagnosis. Sensory behaviours were found to be related to the core features of ASD, to maladaptive behaviours and were found to mediate the relationship between maladaptive behaviours and the core features of ASD, implicating sensory behaviours as having a particularly influential role in the behavioural manifestation of ASD. Further work addressed the lack of research on adults and found high-functioning adults with ASD reported significantly more sensory behaviours than IQ matched typically developing adults. Part 3 explored the measurement characteristics of two definitions of ASD: Wing and Gould (1979) and the new Diagnostic and Statistical Manual for Mental Disorders (DSM-5). A new diagnostic algorithm for DSM-5 criteria using DISCO data was designed and tested. Results showed that when the DSM-5 behaviours were mapped accurately onto a tool that is capable of measuring the spectrum, the DSM-5 criteria were found to have both good sensitivity and specificity. An advantage of the DISCO is the range of behaviours included. Comparison with Wing and Gould’s measure revealed a strong overlap in spectrum concepts and one single element “quality of social interaction” had excellent diagnostic accuracy alone. Finally, in Part 4 the findings from Part 2 and 3 are brought together and discussed and a revised definition of the “autism spectrum” is proposed with regards to a continuum of reciprocal social interaction, which proposes that the pattern of behaviours seen in ASD need to be considered in combination