Annual research review: re-thinking the classification of autism spectrum disorders

Abstract

Background: The nosology of autism spectrum disorders (ASD) is at a critical point in history as the field seeks to better define dimensions of social-communication deficits and restricted/repetitive behaviors on an individual level for both clinical and neurobiological purposes. These different dimensions also suggest an increasing need for quantitative measures that accurately map their differences, independent of developmental factors such as age, language level and IQ.

Method: Psychometric measures, clinical observation as well as genetic, neurobiological and physiological research from toddlers, children and adults with ASD are reviewed.

Results: The question of how to conceptualize ASDs along dimensions versus categories is discussed within the nosology of autism and the proposed changes to the DSM-5 and ICD-11. Differences across development are incorporated into the new classification frameworks.

Conclusions: It is crucial to balance the needs of clinical practice in ASD diagnostic systems, with neurobiologically based theories that address the associations between social-communication and restricted/repetitive dimensions in individuals. Clarifying terminology, improving description of the core features of ASD and other dimensions that interact with them and providing more valid and reliable ways to quantify them, both for research and clinical purposes, will move forward both practice and science.

Figure 1

Illustration of the different conceptual trajectories for the nosology of autism spectrum disorders. The variables of “dimensions of behavior”, “method variance” and “developmental issues” all have significant contributions and must be incorporated and/or considered in any classification of autism.

Figure 2

(a). Existing diagnostic classification according to the DSM-IV for Pervasive Developmental Disorders. (b). Proposed DSM-5 classification dimensions for Autism Spectrum Disorders.

Figure 3

Illustration of convergence of ranges of concern for the toddler Autism Diagnostic Interview-Revised (ADOS) and Autism Diagnostic Interview-Revised (ADI-R) instruments. Reproduced from Kim & Lord (2012a)), with permission.)