Differentiating the Role of Autism Spectrum Disorder and Intellectual Disability in Challenging Behaviors

Background:  Challenging behaviors are frequently reported in both autism spectrum disorders (ASD) and intellectual disability (ID). These behaviors may impede social interactions and learning, and cause harm to the child or others. The relative effects of cognitive level and ASD diagnostic criteria in the occurrence of challenging behaviors are not well understood.

Objectives:  The objectives of this analysis were to differentiate the effects of cognitive level, based on standardized assessment tests, and specific DSM-IV-TR diagnostic criteria for ASD on documented occurrence of challenging behaviors. Both externalizing, i.e., aggressive, argumentative/oppositional, hyperactive/inattentive behaviors and temper tantrums, and internalizing behaviors, i.e., unusual responses to sensory stimuli, unusual fear responses, eating/drinking/sleeping abnormalities, and abnormalities in mood or affect are addressed.

Methods:  Our study population consisted of 8-year old children in 2000, 2006 and 2008 whose special education and clinical records were reviewed as part of the multisite Autism and Developmental Disability Monitoring (ADDM) surveillance network. Children with documented information on cognitive level (6 categories, from profoundly impaired to above average IQ), ASD case status, and presence or absence of DSM-IV-TR criteria and behavioral features associated with ASD were included in the analyses. Multilevel mixed effects logistic regression models, accounting for within-site correlations, were used to estimate crude and adjusted odds ratios (ORs) for each associated behavior. Covariates in the adjusted models include cognitive level, DSM-IV-TR criteria for ASD, sex, race/ethnicity, socioeconomic status and number of autism evaluations.

Results: A total of 10,305 children were included in the analyses. Of these, 5581 (54%) met ADDM case definition for ASD and 4724 children had ASD traits but did not meet case definition.  Of those with ASD, 35% had co-occurring ID. The crude odds of all eight challenging behaviors were significantly greater in children with ASD than in children with ASD traits only (p values < 0.001). In both crude and adjusted models, ORs for mood abnormalities declined with cognitive level, while ORs for unusual fear responses increased with declining IQ. Qualitative impairments in the DSM-IV-TR communication criteria, in general, were associated with lower odds of externalizing behaviors. In particular, a lack of or delayed language (2a) and impaired ability to engage in spontaneous make-believe play (2d) were independently associated with lower odds of externalizing behaviors and lower odds of mood abnormalities. Children with restricted repetitive and stereotyped patterns of behavior generally had increased odds of both internalizing and externalizing behaviors--specifically, those children who demonstrated encompassing preoccupation with stereotyped and restricted patterns of interest (3a) or inflexible adherence to routines or rituals (3b). Persistent preoccupation with parts of objects (3d) was associated with both a threefold increase in the odds of unusual sensory responses and lower odds of aggressive and argumentative/oppositional behaviors. Increased odds of all of the associated behaviors were associated with documented qualitative impairment in social or emotional reciprocity (1d).

Conclusions: Challenging behavioral features associated with ASD are independently associated with intellectual disability and specific ASD diagnostic criteria. Parsing these relationships may increase understanding of these disorders and help achieve improved clinical outcomes.