26835
Investigating the Factors Underlying Discrepancies in IQ and Adaptive Functioning in ASD in the EU-AIMS Longitudinal European Autism Project (EU-AIMS LEAP)

Oral Presentation
Thursday, May 10, 2018: 2:40 PM
Grote Zaal (de Doelen ICC Rotterdam)
J. Tillmann1, T. Banaschewski2, S. Bolte3, J. K. Buitelaar4, A. San Jose Caceres5, C. H. Chatham6, D. V. Crawley5, R. Holt7, E. Loth5, B. Oakley5, E. Simonoff8 and T. Charman9, (1)Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom of Great Britain and Northern Ireland, (2)Child and Adolescent Psychiatry, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany, (3)Center for Neurodevelopmental Disorders (KIND), Center for Psychiatry Research, Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden, (4)Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, Netherlands, (5)Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom, (6)Neuroscience, Ophthalmology, and Rare Diseases (NORD) Roche Pharma Research and Early Development. Roche Innovation Center Basel, Hoffmann La Roche, Basel, Switzerland, (7)University of Cambridge, Cambridge, United Kingdom, (8)King’s College London, Institute of Psychiatry, Psychology and Neuroscience, London, United Kingdom, (9)Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, United Kingdom
Background: Individuals with Autism Spectrum Disorder (ASD) exhibit significant impairments in their adaptive functioning. A recurrent finding is that the level of adaptive functioning is significantly lower than would be expected based on cognitive ability, and that this discrepancy is particularly prominent among higher-ability individuals. This suggests that despite having intact verbal and non-verbal processing skills, many individuals with ASD are having difficulty functionally applying their cognitive strengths to daily contexts. The factors that underlie these discrepancies remain however poorly understood.

Objectives: We investigated IQ-adaptive functioning discrepancies in relation to age, sex, IQ, levels of ASD symptom severity and associated psychiatric symptomatology (e.g. symptoms of ADHD, anxiety and depression) in the EU-AIMS LEAP cohort.

Methods: 299 children and adults with ASD between the ages of 6 and 30 years with IQs varying between 75 and 148 were included in the analysis. First, binary logistic regressions were used to examine predictors of an “IQ-adaptive functioning deficit” across Vineland domains following Duncan & Bishop (2015), whereby a deficit was determined differently for subjects with full-scale IQ (FSIQ) between 75-99 (IQ-Vineland difference score of at least 1SD: ≥ 15) than for subjects with FSIQs ≥ 100 (Vineland domain score falling below the adequate range: i.e. <85). For those that had a deficit as defined above, multivariate regressions were then used to examine predictors of the magnitude of the IQ-adaptive discrepancy.

Results: Across Vineland domain scores, 60-75% of subjects with ASD had an IQ-adaptive functioning deficit (e.g. IQ-Vineland composite discrepancy: M = 30.9, SD = 17.2, Min = -21.1, Max = 78). Model comparisons using binary logistic regression accounting for age, sex and full-scale IQ showed that including ASD symptom measures significantly improved the model fit over and above measures of psychiatric symptom measures, but not vice versa. In relation to unique predictors of an adaptive functioning deficit, we found that higher scores (i.e. greater symptoms) for repetitive/ restrictive behaviours or interests (RBS-R; p from .028 to .007) and greater social communication symptoms (SRS-2; p from .08 to .005), significantly predicted an adaptive functioning deficit across most domains. Conversely, we found little evidence that other psychiatric symptoms affected the likelihood of exhibiting a deficit. Older age and higher FSIQ were significant predictors for adaptive functioning deficits; for the adaptive behaviour composite only, males had significantly higher odds of exhibiting a deficit. For those subjects with a deficit, multivariate regression models demonstrated that higher SRS-2 (p < .001) and higher RBS-R scores (p = .03), but not scores on measures of associated psychiatric conditions, were significant predictors of the IQ-adaptive functioning magnitude.

Conclusions: The findings demonstrate that both the presence/absence of an adaptive functioning impairment in individuals with ASD, as well as the magnitude of such a deficit in relation to cognitive skills, is related to core ASD symptom characteristics more so than to other commonly associated psychiatric symptoms.

See more of: Diagnostic and Adaptive Profiles in Adolescents & Adults with ASD
See more of: Diagnostic, Behavioral & Intellectual Assessment