PROJECT SUMMARY/ABSTRACT Neurodevelopmental processes are shaped by dynamic interactions between genes and environments. Maladaptive experiences early in life can alter developmental trajectories, leading to harmful and enduring developmental sequelae. Pre- and postnatal hazards include maternal substance exposure, toxicant exposures in pregnancy and early life, maternal health conditions, parental psychopathology, maltreatment, structural racism, and excessive stress. To elucidate how various environmental hazards impact child development, it is imperative that a normative template of developmental trajectories over the first 10 years of life be established based on a sufficiently large and demographically diverse sample of the US population. To accomplish this, the Healthy Brain and Child Development National Consortium (HBCD-NC) has been formed to deploy a harmonized, optimized, and innovative set of neuroimaging (MRI, EEG) measures complemented by an extensive battery of behavioral, physiological, and psychological tools, and biospecimens to understand neurodevelopmental trajectories in a sample of 7,500 mothers and infants enrolled at 24 sites across the United States (US). The HBCD-NC will carry out a common research protocol under direction of the HBCD- NC Administrative Core (HCAC) and will assemble and distribute a comprehensive and well-curated research dataset to the scientific community at large under the direction of the HBCD-NC Data Coordinating Center (HDCC). The overarching goal of the HBCD-NC is to create a comprehensive, harmonized, and high- dimensional dataset that will characterize typical neurodevelopmental trajectories in US children and that will assess how biological and environmental exposures affect those trajectories. A special emphasis will be placed on understanding the impact of pre- and postnatal exposure to opioids, marijuana, alcohol, tobacco and/or other substances. To address these broad objectives, the sample of women enrolled will include: 1) a racially, ethnically, and socioeconomically diverse cohort that is representative of the US population; 2) pregnant woman with use of targeted substances (opioids, marijuana, alcohol, tobacco); and 3) demographically and behaviorally similar women without substance use in pregnancy to enable valid causal inferences. In addition, the HBCD-NC will identify key developmental windows during which both harmful and protective environments have the most influence on later neurodevelopmental outcomes. The large, multi- modal, longitudinal, and generalizable dataset that will be produced for the first time by this study will provide novel insights into child development using state-of-the-art methods. The HBCD-NC study will inform public policy to improve the health and development of children across the nation.

PROJECT NARRATIVE Various adverse and protective environments may affect child development. The Healthy Brain and Child Development National Consortium (HBCD-NC) will follow 7,500 mothers and their children from 24 locations across the U.S. from before birth to 10 years of age to better understand which harmful and protective environments exert the greatest impact on child development. This study will help to improve the health and development of children across the nation.