Component A: Study to Explore Early Development (SEED) Follow up Studies

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder affecting >1.5% of children in the United States. Individuals with ASD experience deficits in social communication along with restricted interests or repetitive behavior. The severity and patterns of symptoms can vary greatly and be lifelong in duration. It is

unclear how the presentation of ASD changes from early childhood into adolescence or adulthood. The causes of ASD are also unknown, though substantial evidence supports the contribution of both genetic and environmental factors. Major gaps in knowledge exist because US studies to date have lacked the sample

size, depth of data collection, or appropriate life course timing to address important questions. The Study to Explore Early Development (SEED) is now poised to overcome these limitations. SEED is a large case-control study of children ages 2-5-years and their families, implemented across eight states over three phases. SEED

collected detailed data on children's core ASD symptoms, cognitive status, and presence of co-occurring conditions in early childhood, along with extensive risk factors related to maternal health and the perinatal environment as well as genomics. The SEED sample includes ~2,044 children with ASD, 1,950 with non-ASD

developmental disabilities (DD), and 2,285 population control children (POP), making this the largest etiologic study of ASD in the US. Recent ancillary studies - the SEED Teen Pilot and SEED COVID studies -- will soon add data on adolescent health and the consequences of the pandemic, respectively, for some SEED

participants. The work proposed here, SEED Follow-up Studies (SEED FU), will maximize the impact of extant SEED data through analyses that characterize ASD phenotypes and assess the potential interplay between genetic and other risk factors. SEED FU will also facilitate new data collection in middle childhood,

adolescence and early adulthood to characterize changes in ASD phenotype across developmental stages, and the associated health, educational, and service needs across the early life course. These data will further enable prospective analyses of associations between early life factors and later childhood through early

adulthood outcomes. Studying risk factors in relation to life course phenotypic subgroups may also help elucidate etiologies previously masked in ASD case-control studies. The WI SEED Team in combination with the SEED Network's collaborative infrastructure and extensive extant data resources, will ensure the

successful implementation of the SEED FU Study in Wisconsin and contribute to success across the network. SEED is well powered to make significant contributions to our understanding of the complex autism phenotype and identifying factors associated with ASD risk in the population. The knowledge gained by SEED FU will

greatly advance our ability prevent adverse developmental outcomes and to support individuals with ASD and their families to ensure optimal wellbeing through early adulthood.