Patterns of Symptom Severity Developmental Trajectories in Children with Autism Spectrum Disorder in Taiwan

Background: Autism spectrum disorder (ASD) is widely known to be a highly heterogeneous neurodevelopmental disorder. Recently growing bodies of researches focused on the developmental trajectories of autism severity, which has been seen as one ofpromising waysto understand the heterogeneity of ASD and may lead to a better understanding of prognosis (Baker, Smith, Greenberg, Selzer & Taylor, 2011). However, seldom longitudinal studies have been conducted in the East, and none in Taiwan. Therefore, it highlights the necessity of the investigation.

Objectives: The purpose of this study is (1) to explore the subgroups of autism severity in the children with ASD from toddlers to school age in Taiwan, (2) and further characterize these subgroups by cognitive and adaptive functions.

Methods: Seventy ASD participants were assessed at three time points from toddlerhood to school age (mean age: T1 = 35.11 months, T2 = 55.11 months, T3 = 109.17 months) across 6 years. The standardized assessments were used to measure autistic total symptoms severity (ADOS calibrated severity score [CSS]), cognitive functions (MSEL, WPPSI-IV or WISC-IV) and adaptive functions (VABS-II). The hierarchical cluster analysis collocated with two-way mixed designed ANOVA were conducted to identify the subgroups of three time points ADOS-CSS. The comparison of cognitive and adaptive functions between subgroups were showcasedby one-way ANOVA.

Results: In hierarchical cluster analysis, three subgroups were identified including “worsening group” (n = 43), “persistent high group” (n = 18), and “improving group” (n = 9). All groups improved on FSIQ, but the worsening and improving groups show significantly higher progress than does the persistent high group (p = .016*). The improving group has higher but no significant difference in T1 FSIQ (p = .060). In T3, the improving group has the highest cognitive outcome (p= .001**). In terms of adaptive functions, three groups show significant differences in Vineland adaptive behavior composite (improving > worsening > persistent high; p = .000***). The improving group has the best performance in the communication (improving > worsening > persistent high; p = .000***) and daily living skill (improving > worsening = persistent high; p = .005**) domains, but not in the socialization domain (improving = worsening > persistent high; p = .000***).

Conclusions: Similar to western findings, the development of autism severity can bedivided into three groups. Each group is characterized by different cognitive and adaptive functions, which shows total symptoms severity is a valid indicator for Taiwanese children with ASD. Three groups have similar FSIQ in toddlerhood, and all of them show improvement over time. But the greater improvement in the improving and worsening groups might contribute different outcomes in school age, of which the improving group has the highest FSIQ, followed by the worsening group, and the persistent high group, which has the lowest FISQ. The improving group also shows the best performance in adaptive functions in school age; however, the advantage mainly appears in the communication and daily living skill domains, but not in the socialization domain, which might reflect the existence of ASD social deficit.