Saturday, May 9, 2009: 2:00 PM
Northwest Hall Room 1 (Chicago Hilton)
P. Szatmari
,
The Offord Centre for Child Studies, McMaster University, Hamilton, ON, Canada
S. Georgiades
,
Offord Centre for Child Studies, McMaster University, Hamilton, ON, Canada
S. E. Bryson
,
Pediatrics and Psychology, Dalhousie University/IWK Health Centre, Halifax, NS, Canada
E. Duku
,
Offord Centre for Child Studies, McMaster University, Hamilton, ON, Canada
W. Roberts
,
Department of Pediatrics, Hospital for Sick Children & Bloorview Kids Rehab, University of Toronto, Toronto, ON, Canada
E. Fombonne
,
Head, Division of Child Psychiatry, McGill University, Montreal, QC, Canada
P. Mirenda
,
Educational and Counseling Psychology and Special Education, University of British Columbia, Vancouver, BC, Canada
I. M. Smith
,
Pediatrics & Psychology, Dalhousie University & IWK Health Centre, Halifax, NS, Canada
T. Vaillancourt
,
University of Ottawa, Ottawa, ON, Canada
J. Volden
,
Speech Language Pathology, University of Alberta, Edmonton, AB, Canada
C. Waddell
,
Simon Fraser University
L. Zwaigenbaum
,
Department of Pediatrics, University of Alberta, Edmonton, AB, Canada
A. P. Thompson
,
The Offord Centre for Child Studies, McMaster University, Hamilton, ON, Canada
N. Garon
,
Autism Research Centre, IWK Health Centre, Halifax, NS, Canada
.. Pathways in ASD Study Team
,
McMaster University, Hamilton, ON, Canada
Background: Autism is neurodevelopmental disorder characterized by symptoms of social and communication impairment and by the presence of repetitive, restricted, stereotyped behaviours. The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM IV) organizes these symptoms in three distinct, mutually exclusive categories and criteria in each must be met to qualify for a diagnosis of autism. This conceptualization, which is based primarily on clinical judgment, has failed to capture the variability and complexity of the clinical presentation of autism. Recent factor analytic studies support the idea of using a dimensional as well as a categorical approach to conceptualizing autism. However, these studies have focused on a single symptom-based instrument (the Autism Diagnostic Interview Revised; ADI-R) and a single informant.
Objectives: The main objective of this study is to examine the structure of an expanded autism phenotype that, in addition to symptoms, includes information derived from other sources and methods.
Methods: The sample consisted of 255 preschool children with a clinical diagnosis of autism participating in a Canadian longitudinal study (Pathways in ASD). Scores from multiple parent-report and direct observational sources, including diagnostic (ADI-R), language (Preschool Language Scale Fourth Edition; PLS-4), adaptive functioning (Vineland Adaptive Behavior Scales Second Edition; VABS-II), and behavioural (Child Behavior Checklist; CBCL 1.5/5 & Repetitive Behavior Scale Revised; RBS-R) measures were used in exploratory factor analysis.
Results: A three-factor solution explaining 63.70% of the variance was selected based on the scree plot criterion and conceptual interpretability. The three factors were labeled maladaptive behaviours (MB), containing repetitive behaviours and internalizing and externalizing behaviours, general level of functioning (GLF), reflecting adaptive behaviours from the VABS-II and language scores from the PLS-4, and social-communication symptoms (SCS), representing those domains from the ADI-R.
Conclusions: Based on these findings, we propose a new multidimensional model for the phenotypic structure of behaviours, functional level and symptoms in young children with autism. The use of quantitative severity indices on the three latent dimensions (MB, GLF, & SCS) appears to capture the phenotypic diversity of autism in a parsimonious yet comprehensive way.
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