The Relationship Between Intellectual Profiles, ASD Symptoms, and Age in a North American Sample of Youth with Autism Spectrum Disorder



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Autism spectrum disorder (ASD) is an increasingly common neurodevelopmental disorder, estimated to occur in 1 of 68 individuals (Centers for Disease Control and Prevention [CDC], 2014). Evaluation of intellectual functioning is one component of a comprehensive evaluation for individuals with ASD and, specifically, is necessary for differential diagnosis, prognosis and selection of appropriate interventions (Filipek et al., 2000; Johnson & Myer, 2007; Klin, Saulnier, Tsatsanis, & Volkmar, 2005; Kuschner, Bennetto, & Yost, 2007; Volkmar et al., 2014). Profiles of scores on measures of intellectual functioning have the potential to aid in further understanding etiology of ASD. Research investigating the relationship between ASD symptoms and scores on measures of intellectual functioning suggests that scores on the factors comprising global measures of intellectual functioning may be related to ASD symptoms (Black, Wallace, Sokoloff, & Kenworthy, 2009; Joseph, Tager-Flusberg, & Lord, 2002). However, to date, such research has been limited by methodological problems such as the use of samples identified using unreliable subtypes of ASD (i.e., subtypes identified in the Diagnostic and Statistical Manual, 4th Edition - Text Revision (DSM-IV TR; APA, 2000) and an overreliance on variable-centered methodological strategies. This study was designed to further elucidate the relationship between scores on measures of intellectual functioning (i.e., profiles of intellectual functioning), ASD symptoms, and age. The methodology of the study was primarily designed to address previous weaknesses by applying person-centered statistical methods (i.e., latent profile analysis [LPA]) to investigate profiles of intellectual functioning in youth with ASD using a recommended measure of intellectual functioning, the Differential Ability Scales – Second Edition (Elliott, 2007a). A secondary purpose of the current study was to investigate whether age predicts profiles of intellectual functioning and to investigate whether profiles of intellectual functioning predict patterns of core ASD symptoms (i.e., social-communication and restricted/repetitive interests or behaviors).
The sample (n=2121) was extracted from a sample of 2644 youth, between the ages of 4 and 18, who have relevant data points in the Simons Simplex Collection (SSC). The SSC is a multi-site, genetic research project in North America that includes families with only one child with an ASD and no other first- through third-degree relatives with ASD or suspected ASD (i.e., simplex families; Fischbach & Lord, 2010). The individuals included in the project are well characterized and the data points included for each individuals have been scrutinized at multiple levels. In order to be included in the SSC, youth necessarily met criteria for an ASD (per DSM-IV-TR criteria) based on scores from standardized diagnostic instruments and clinical opinion.
LPA models suggested that a five-class solution was the best model fit for all samples (i.e., the whole sample, the early-years sample, and the school-age sample). Multinomial logistic regression models with age and measures of core ASD symptoms as predictors were significant for all samples; but, the predictive value of those measures were variable when considering the individual classes within the five-class models. The current study adds to the existing literature base by using person-centered statistical methods to clarify the relationship between profiles of scores on measures of intellectual functioning, ASD symptoms, and age. Clinical implications, limitations, and future directions are discussed.



Autism spectrum disorder (ASD), Cognition, Age