Contribution of Executive Function to Adaptive Behavior Changes over Time

Background:   The development of daily living skills, or adaptive behavior, is particularly challenging for children with ASD. Klin et al. (2007) reported substantially lower adaptive ability compared to cognitive ability in children with high-functioning autism spectrum disorder (HFASD). Specifically, adaptive behavior (social and communication skills) showed a marked decrease with age when examined in a cross sectional manner (Klin et al., 2007). However, conclusions regarding age trends need further study using longitudinal designs. Additionally, it is unclear what factors drive change in adaptive behavior over time. Prior research has demonstrated a relationship between executive functioning and adaptive behavior, such that impairments in executive abilities are strongly associated with deficits in communication, play and social relationships found in children with autism (Gilotty et al., 2002). However, longitudinal research has not confirmed this finding.

Objectives: We sought to determine whether children with HFASD demonstrate longitudinal change in adaptive behavior, and whether baseline executive function predicted such change. 

Methods: Participants consisted of 46 children with HFASD (38 male) evaluated through a hospital-based neuropsychology service on two occasions separated by at least six months (M=3.24 years, SD=1.46 years). Complete data on the Vineland Adaptive Behavior Scales (VABS) and Behavior Rating Inventory of Executive Function (BRIEF) were available at both time points. Participants ranged in age from 3 to 16 years at the first assessment (M=8.41, SD=2.83), and received a score of at least 70 on either verbal or performance IQ (full scale IQ M=102.08, SD=21.54). Reliable change indices (RCI) were calculated for composite and domain scores on the VABS for each participant. Clinically significant improvement or deterioration was based on the 95% confidence interval. A multiple regression analysis was conducted to determine whether global executive functioning at time 1, measured by the BRIEF, predicted change in adaptive behavior after accounting for baseline adaptive behavior and full scale IQ. 

Results: RCI results indicated 11 participants improved, 7 participants deteriorated, and 23 participants did not change in their standard scores. When participants were divided into two groups based on RCI improvement, no significant differences were found between participants who improved and those who did not improve in regards to age, gender, IQ, or executive function. However, results from the regression model indicated time one VABS Composite score (ß=-0.80, t(34)= -4.86, p<.001), time one BRIEF global score (ß= -0.33, t(34)=-2.05, p<.05), and full scale IQ score (ß=0.36, t(34)=2.65, p<.05) explained 42.2 percent of the variance in the VABS Composite change score (F(3,34)=8.26, p<.001).

Conclusions: In the first longitudinal investigation of adaptive functioning in children with HFASD, we found that approximately one quarter of the participants demonstrated growth in standardized VABS scores over time and that executive function abilities, intelligence, and baseline adaptive skill level were all predictive of positive change. These findings have implications for the importance of targeting adaptive skills, and executive functions that contribute to them, in children with HFASD.D.