Objectives: The main objectives of this study were to (a) develop a measurement model of indicators reflecting social- communication symptoms and functioning in children with ASD; and (b) examine the developmental course over 12 months of these empirically derived factors.
Methods: The sample consisted of 273 newly-diagnosed preschool children (mean age: 40.11; SD = 8.82; 233 males) with ASD participating in a longitudinal study. A total of 12 indicators from three instruments: Vineland Adaptive Behaviours Scale (VABS II), Preschool Language Scale (PLS-4), and Social Responsiveness Scale (SRS), were used in exploratory factor analysis. Then, the empirically derived factor scores were used in trajectory analysis to identify distinct mixtures of trajectories within the sample over 12 months.
Results: The structure of social-communication in this sample is best represented using a two-factor solution, explaining 72.45% of the variance. Factor I, Social-Communication Functioning, includes indicators from the VABS II and the PLS-4. Factor II, Social- Communication Symptoms, includes indicators from the SRS. Both factors have acceptable internal consistency. Results indicate that there are three distinct functioning trajectory groups, all of which have statistically significant inclining trajectories (p<0.05) suggesting all children are improving in their social-communication functioning, but at very different rates. Furthermore, there are statistically significant differences in developmental level between children across the three groups. In the case of social-communication symptoms, results also show that there are three distinct trajectory groups (high, low, and intermediate symptoms). The intermediate group has a statistically significant declining trajectory (p<0.05) while the end groups (i.e., high and low) have flat trajectories. In the case of the Social-Communication Symptoms, there are no differences in developmental level between children across the three groups.
Conclusions: Findings from this study suggest that (a) social- communication functioning and symptoms are independent dimensions in ASD; (b) trajectory models of social- communication over 12 months reveal 3 groups of preschoolers with ASD who “start off” at different levels of functioning and symptoms; and (c) social-communication functioning improves over time in the first 12 months after diagnosis, with the greatest improvement in those with higher initial functioning. Social-communication symptoms remain relatively unchanged, with some improvement only in the intermediate-severity group. These findings have important implications for informing parents and front-line clinicians about change in ASD children over the first 12 months post-diagnosis in the pre-school years.
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