Despite considerable research on marijuana use, there are many discrepancies and insufficient research has been conducted to disentangle the potential neurocognitive consequences of marijuana use from its neurocognitive precursors. Thus, it is unknown whether some of the """"""""consequences"""""""" of marijuana use identified in adult populations using retrospective designs actually predated use, acting as vulnerability factors that are subsequently exacerbated by the eventual use of marijuana. Moreover, there are no studies of the developmental progression of neurocognitive skills in adolescent marijuana users relative to nonusers and users of other drugs. Many studies report that severe and chronic marijuana use is associated with impairments in executive cognitive functions (ECF) and affect regulation in adults. It is possible that development of these skills may be subtly delayed during adolescence when onset commonly occurs and the brain is most vulnerable to developmental perturbations. Vulnerability to developmental delays may be particularly pronounced when marijuana use occurs early in adolescence and is frequent. Although the adolescent brain is highly vulnerable to environmental insults, its plasticity provides an opportunity to alter pathways to negative outcomes using well-targeted interventions. A better understanding is needed of neurocognitive factors that influence onset and levels of eventual marijuana use and delineation of how these factors may be exacerbated by damage potentially caused by marijuana use. To address these critical issues, the proposed longitudinal study will identify specific neurocognitive factors that antedate and predict marijuana use and assess developmental change in these factors as preadolescent children age into a period when onset of marijuana use is common. Further, the putative neurocognitive consequences of marijuana use, controlling for pre-use conditions, will be isolated from precursors. Preadolescents who are 10, 11, and 12 years old (n=600) who have not yet used marijuana and a corresponding primary caregiver for each child will be recruited from a community with very high rates of early marijuana use to ensure a sufficient sample of eventual users. Participants with no history of drug use will be assessed at baseline and 3 subsequent annual waves, spanning the period of initiation and escalation for this early and high prevalence population. Developmental factors and their interaction with marijuana use overtime will be examined using an empirically guided and developmentally appropriate neurocognitive task battery and comprehensive interview. The potential moderating role of psychological disorders (e.g., anxiety, depression, ADHD) and gender will be assessed and adjustments will be made for co-occurring drug use, socioeconomic status, IQ, pubertal development, neighborhood conditions, and parental substance abuse disorder. Elucidation of these developmental vulnerabilities and consequences in a longitudinal panel design can inform the design of targeted interventions for adolescent marijuana users.