drug exposures in as much detail as possible with respect to the specific substance, quantity/frequency, dosage, potency, and route of administration. Consequently, considerable time was spent developing a detailed lifetime use and TLFB interviews that took these parameters into consideration. However, we are mindful of the fact that at the initial stages of the ABCD Study, drug exposures are likely to be minimal in this young cohort; thus, we included measures designed to be sensitive to low-level exposures (e.g., sipping alcohol, first puffs of cannabis and nicotine) in order to be able to track the trajectories of substance involvement for all participants. Similarly, substance use does not arise in a vacuum so we are attentive to those social/interpersonal (drug availability, descriptive norms, family rules) and individual (e.g., outcome expectancies) that presage initial and later use. At the same time, for that small minority of participants who do engage in early substance use (i.e., assessed at baseline), we are poised to capture both acute drug effects (e.g., subjective effects), various harms (e.g., individual, neurocognitive, and social consequences) as well as SUD symptomatology and diagnosis (see ABCD Mental Health module). In this way, we hope to be able to portray substance use
