Adaptive Behavior Challenges Increase Into Young Adulthood and Are Predicted by Parent‐Reported Executive Function in Autistic Youth

Everyday adaptive behavior skills are a strong predictor of independence, mental health, and quality of life for autistic people. However, autistic individuals' adaptive skills are typically below expectation for their age and their intellectual abilities. Executive function is related to concurrent adaptive behavior, but few longitudinal studies have evaluated it as a predictor of adaptive behavior development over time. This study examines the trajectories of parent-reported adaptive behavior skills in autistic youth from early childhood to young adulthood and their relationship to parent-reported flexibility, working memory, and inhibition challenges. Leveraging a longitudinal sample of 313 participants (age range = 2-25 years; 64 females; Full Scale IQ: M = 103.3, range = 52-159; number of visits per participant: M = 3.01, range = 2-9) across a total of 941 visits, we examined trajectories of adaptive skills and their relationship to executive function challenges using multilevel growth curve modeling. Age-related adaptive skills decline with age in autistic people from 2 to 25 years old, regardless of parent education level. Parent-reported executive function challenges predict adaptive behavior scores across all adaptive skill domains. Adaptive behavior challenges endure across development for autistic people. Executive function is a key factor in adaptive outcomes, making it an important target for intervention and environmental supports.