PROJECT SUMMARY/ABSTRACT ? RESEARCH COMPONENT The goal of this study entitled, ?Sleep and Circadian Dysfunction, Brain and Neurobehavioral Development in Autism? is to examine how disturbed sleep and altered circadian rest/activity rhythms (RARs) affect brain development, cognitive and adaptive function, and symptom severity in children with autism. Disturbed sleep is highly prevalent among children with autism spectrum disorder (ASD); over 60% are estimated to exhibit frequent sleep disturbances, including delayed sleep onset, fragmented nighttime sleep, and early-morning waking. While typically viewed as a consequence of ASD, disturbed sleep may not only have acute effects on cognition, adaptive functioning, and behavioral disturbances in this population. Notably, while many studies have evaluated the relationship between disordered sleep and neuroimaging, and neuroimaging and ASD, no work, to our knowledge, has integrated these topics. Furthermore, rigorous comparison of sleep and RAR metrics via parent-report and actigraphy have not been conducted in ASD. For this project, we propose to address these gaps through refining how sleep/wake problems are assessed in children with ASD by applying novel statistical modeling to both objective (using actigraphy) and parent-report (using CSHQ) measures and examining how disturbed sleep and altered RARs might affect brain structure and function in children with ASD. We embed this project in the Kennedy Krieger Institute-Johns Hopkins University Intellectual and Developmental Disabilities Research Center (IDDRC), leveraging crucial resources in phenotypic assessment, neuroimaging, biostatistics, and behavioral preparation for procedures that are available through the Center. At the same time, this investigative team brings new statistical and epidemiologic expertise to Center Cores, to conduct this study in 200 children with and without ASD. Via this project, Center resources will be used to further integrate this population with 493 children with extant data (but not wrist actigraphy), establishing a large-well phenotyped population for Center research. This work will help to refine and inform clinical and prevention practices among children with disordered sleep and ASD, providing methodological advances in sleep characterization and etiology.