Our proposal is responsive to the Funding Option A of the current CDC RFA-CE-23-006. An average of some 15,000 teenagers 12 to 19 years old died annually in the United States. The 3 leading causes of death among teenagers were unintentional injuries, homicide, and suicide. Among these fatal youth injuries, most homicides were gun related (83%), and about half of suicides involved a gun (45%). The resulting injuries, medical cost, and years of potential life lost are all part of significant public health burden of firearm violence to our society. Research has consistently shown that youth gun violence is influenced by individual-level risk factors including demographics including gender, race and ethnicity, mental health conditions, interpersonal relationships, accessibility of lethal means, and experience of youth bullying. While the focus on individual-level risk factors is valuable, little is known about the impact of broader youth-focused health policies in affecting youth gun violence, including state bullying policies and firearm policies, and how they may interact in affect youth violence especially involving guns. Consistent with the Prevention Paradox, the social ecological model emphasizes that an individual is embedded within a social context; therefore, it is critical to understand how social-contextual factors especially health policies influence youth firearm violence. The objective of our proposal is to improve the evidence base for youth firearm prevention by conducting a comprehensive multilevel evaluation with the use of propensity score matching and synthetic control methods to assess the confluence of state-level bullying policies and firearm policies on reducing youth gun carrying and firearm- related fatality from 1999 to 2021. Youth gun carrying data will be based on state-based Youth Risk Behavior Survey data, and youth firearm fatality data will be based on vital statistics. Our aims include: Aim 1: evaluate the impact of the overall state bullying policies environment and assess the relative effectiveness of specific bullying policy component on youth gun carrying and firearm death; Aim 2: evaluate the impact of the overall state firearm policies environment and assess the relative effectiveness of youth-oriented firearm policies on youth gun carrying and firearm death; Aim 3: assess whether state bullying policies environment interacts with state firearm policies environment in affecting youth gun-carrying and firearm death; Aim 4: explore potential cross-level interactions between state-level policies and high risk target populations (e.g., depression; binge drinking; suicidal attempt; racial/ethnic minority; gender minority group) in affecting youth gun carrying. Our in- depth investigation on these already collected data will provide evidence on the relative effectiveness of policy strategies in reducing youth firearm violence, and how these youth-specific policies have differential impact on certain high-risk youth p...