One of the goals of the ABCD Study is to characterize youth prior to the initiation of significant substance use. Adolescence is a period of ongoing neurodevelopment that is linked with an increase in risk-taking behaviors, including the onset of substance use (Casey et al., 2008; Eaton et al., 2006; Gardner and Steinberg, 2005; Casey et al., 2000; Giedd et al., 1996; Gogtay et al., 2004; Lenroot and Giedd, 2006; Sowell et al., 2004, Sowell et al., 1999, Sowell et al., 2002; Mills et al., 2014; Schmitt et al., 2014; Houston et al., 2014). Initiation of drinking alcohol (beyond a sip) and use of most illicit substances typically begins in the early teen years, although high-risk demographic communities report initiating use during the elementary and early middle school years (Feldstein Ewing et al., 2015). In the U.S., among 8th graders (13–14 year olds), lifetime use of alcohol (22.8%), electronic cigarettes (17.5%), cannabis (12.8%), tobacco cigarettes (9.8%) inhalant (7.7%), prescription amphetamines (5.7%) and prescription tranquilizers (3.0%) are the most commonly used substances (Johnston et al., 2017). Data is unavailable for 8th
