As more states have legalized the recreational use of marijuana, its use among adolescents is increasing. This is problematic because marijuana's psychoactive component, THC, can act directly on parts of the brain in critical development during adolescence. Current literature proposes long-term cognitive effects based on recurring correlations; however, a lack of consistent and reliable approaches for controlling confounding variables remains an issue. This review will focus on the current state of research on the effects of adolescent marijuana use on cognitive function, its potential long-term consequences, and highlight the inconsistencies in research methodologies.