Developmental Changes in Symptoms and Adaptive Functioning in Autism Spectrum Disorder: A Real-World Longitudinal Perspective

Objective To evaluate longitudinal changes in adaptive functioning measured by the Korean Vineland Adaptive Behavior Scales, Second Edition (K-VABS-II) in children with autism spectrum disorder (ASD) receiving routine outpatient care.Methods This retrospective study analyzed data from 156 children (aged 2–7 years) who completed at least two K-VABS-II assessments at a tertiary university hospital. Additional evaluations included the Korean version of the Childhood Autism Rating Scale, Second Edition- Standard Version (K-CARS2-ST) and the Beery–Buktenica Developmental Test of Visual–Motor Integration, Sixth Edition (VMI-6).Results The K-VABS-II Adaptive Behavior Composite score declined significantly from a baseline of 56.07 to 54.10 (p<0.05) over an average interval of 24.14 months. Daily living skills and socialization showed the most pronounced reductions (p<0.001), while communication and motor skills remained stable. VMI-6 scores also declined significantly (p<0.05), while K-CARS2-ST scores showed no meaningful change (p=0.859).Conclusion Longitudinal evaluations using the K-VABS-II revealed significant declines in adaptive functioning among children with ASD, even when core symptom severity remained stable. These findings highlight that functional development may follow a divergent path from symptom trajectories and remain vulnerable to regression without adequate support. This underscores the critical need for early and sustained interventions to promote adaptive outcomes and the urgent development of innovative pediatric therapeutics.Trial Registration: Clinical Research Information Service Identifier: KCT0010881