Background: Sedentary lifestyles, particularly high screen time, have been increasingly associated with mental health issues such as anxiety and depression among youth. Understanding these associations is crucial for developing effective interventions.Objective: This review aimed to assess the relationship between sedentary lifestyles and mental health outcomes, focusing on anxiety and depression in young populations globally.Methods: A comprehensive search of PubMed, Google Scholar, and APA PsycInfo was conducted using keywords such as "sedentary lifestyle," "screen time," "anxiety," "depression," and "mental health." Studies included cross-sectional, longitudinal, systematic reviews, and randomized controlled trials. Data on odds ratios, prevalence rates, and statistical connections were extracted and synthesized, following the PRISMA guidelines for narrative reviews.Results: The review included 40 studies published from 2011 to 2024. Findings indicated that screen time-related inactivity rates ranged from 23.2% to 62%, with depression prevalence between 15% and 25%, and anxiety prevalence from 10% to 20%. High screen time was strongly associated with increased mental health risks.Conclusion: Sedentary behavior and high screen time significantly impact youth mental health, emphasizing the need for targeted public health interventions to reduce screen time and promote active lifestyles.