The Adolescent Brain Cognitive Development (ABCD) Study is the largest longitudinal study of brain development and child health collecting data from more than 11,000 children across the U.S. beginning when they are 9-10 years old and continuing for a decade. In addition to behavioral assessments, youth undergo neuroimaging and provide biospecimens, including saliva for hormone analysis, urine and hair for substance use and exposure, deciduous teeth for environmental exposure, and blood for genetic analysis and met...