Policymakers, parents, educators, and researchers increasingly want to know what the implications of adolescent substance use are for the developing brain, including how it affects life outcomes such as academic success and career achievement, as well as long-term mental and physical health. For instance, marijuana use by adults is increasingly accepted in our society, and as of this writing, most Americans live in a state where it is either legal for adult recreational use or available for medical use (National Conference of State Legislatures, 2017). At the same time, new synthetic drugs including cannabinoids (e.g., “Spice” products), cathinones (“bath salts”), and opioids (U-47700, W-18) have been emerging, often faster than authorities can monitor and control them. Novel ways of taking drugs (e.g., dabbing and edibles for marijuana) and new technologies such as electronic nicotine delivery systems (ENDS) are rapidly transforming how youth and adults use drugs, and raise different questions about how multiple substances interact to affect brain development. In addition, while the percentage of adolescents and young adults consuming alcohol has decreased, emergency department visits and hospitalizations related to
