Predictors of Adaptive Functioning and Internalizing and Externalizing Symptoms in Children with Autism Spectrum Disorder (ASD)

Background: Adaptive skills and maladaptive behaviors are important indices of a child’s functioning. The existing literature has consistently demonstrated adaptive functioning deficits (Kanne et al., 2011) and a high prevalence of externalizing symptoms (e.g. aggression and hyperactivity) in children with ASD (Matson et al., 2009; Mayes et al., 2012). There is also evidence of elevated levels of internalizing symptoms (e.g., anxiety and depression) in this population (Mayes et al., 2011). Severity of autistic symptomatology and cognitive ability have been associated with adaptive skill delays (Klin et al., 2007; Lopata et al., 2012) and elevated levels of internalizing and externalizing symptoms (Jang et al., 2011; McTiernan et al., 2011), but these results have been inconsistently observed.

Objectives: We examined predictors of adaptive functioning, internalizing symptoms, and externalizing symptoms in a large sample of children with ASD. Our study is one of the first to include internalizing and externalizing symptoms as predictors of adaptive functioning. It is also one of the first to examine the predictors of maladaptive behavioral symptoms, particularly the less-studied internalizing symptomatology, in this population. 

Methods: Participants included 200 children (6-17 years) with ASD. Cognitive abilities were assessed using the DAS-II (n = 193), WISC-IV (n = 5), or WASI (n= 2) (IQ = 91.9 ± 20.9, range = 50-146). Measures of autism symptom severity, internalizing and externalizing symptoms, and adaptive functioning were obtained from caregiver reports (Social Responsiveness Scale; SRS, Child Behavior Checklist; CBCL, and Vineland-II; VABS-II, respectively).

Results: Seventy-six participants (38%) exhibited marked elevations (T-score > 65) in internalizing symptoms, and 39 (19.5%) exhibited elevated externalizing symptoms, as measured by the CBCL Internalizing and Externalizing Problems domain scores. Adaptive functioning, measured by the VABS-II Adaptive Behavior Composite, was 75.9 ± 9.0 (range = 54-102), indicating that on average, our sample demonstrated significantly delayed adaptive skills. We conducted three structural equation analyses with adaptive functioning, internalizing symptoms, and externalizing symptoms as the dependent variables. More severe autistic symptomatology and lower IQ predicted more impaired adaptive functioning. Greater autism symptom severity and higher IQ predicted internalizing symptoms, while externalizing symptoms were predicted only by autism symptom severity. Though adaptive functioning was significantly correlated to both internalizing and externalizing symptoms, it was not predicted by, and did not predict, either symptomatology. Subsequent analyses will include an examination of the effects of child age on the generalizability of our findings.

Conclusions: Results suggest that autism symptom severity and cognitive ability are important factors in explaining individual differences in adaptive functioning, internalizing symptoms, and externalizing symptoms. Continued study is needed on the factors contributing to impairment in these domains, as they directly impact the daily lives of families and children with ASD. As we aim to improve long-term outcomes for these children, understanding the relationships between these areas of functioning may encourage and inform interventions that address both the factors that contribute to adaptive and behavioral functioning impairments and the deficits themselves.