This application is a supplement to the Latinx Health in Rural Areas project (R01DA048827) that applies prevention science paradigm to examine etiology of substance use and related individual, family, and community risk and protective factors among rural Latinx adolescents and young adults. The supplement will extend the parent project into the area of mental health and examine the dynamic interplay between depression and anxiety and substance use over the course of adolescence and young adulthood among rural Latinx youth, an underserved and marginalized population that has grown rapidly in recent years. The long- term career goal of the candidate, Ms. Griselda Martinez, is to become an independent investigator that integrates developmental models of substance misuse and factors that promote health equity in this population. The primary objective of this supplement is to understand the developmental links between substance use and mental health using a cultural-developmental lens to inform potential prevention and intervention targets and their timing. These objectives will be accomplished in two specific aims that: (1) examine the reciprocal and longitudinal associations between depressive symptoms and substance use over the course of adolescence, and the extent to which there are differences in these associations between rural Latinx youth from immigrant vs. U.S.-born (3rd gen) families and between 3rd generation rural Latinx youth and non-Latinx Whites. Sex differences, externalizing symptomatology, and risk and protective factors from multiple domains will be tested. For instance, family-level factors, including family bonding and family conflict that may change with acculturation will be examined. (2) Examine links between internalizing symptomatology (depression and anxiety) and substance use in young adulthood and determine the extent to which there are differences in the comparison groups of interest. Systemic barriers such as lack of access to healthcare will also be examined. The candidate will conduct the research under the supervision of Dr. Katarina Guttmannova, PhD, and the parent grant’s team of Co-Is across three multidisciplinary sites to gain expertise in developmental models of substance misuse beyond alcohol and health disparities research, deepen her proficiency with longitudinal methodologies, and lay groundwork for future independent research funding. Training activities include mentorship meetings, advanced statistics seminars, consultation with leading researchers on etiology of substance misuse and related health risk behaviors, and grant writing. This supplement will allow the candidate to dedicate her time to the proposed activities aimed at establishing independence as an investigator, which will thereby increase the number of underrepresented research faculty conducting research in the field of drug abuse research.