Abstract: Permit-to-purchase (PTP) laws for handguns are state-level policies that creates a robust system to restrict access to guns by prohibited individuals and deter straw purchasing (i.e., when someone who is not prohibited buys a gun for someone else). PTP laws address weaknesses in federal laws by extending background check requirements to all gun sales and establishing an application process that involves the purchaser directly engaging law enforcement and undergoing a more rigorous background check. Prior evaluations of PTP laws suggest they are effective at reducing diversions of guns for use in crime through straw purchasing, and homicide and suicide by firearm. To date, evaluations of PTP laws have primarily focused on population impacts at either the state- or county-level. This study seeks to extend our understanding on the effectiveness of PTP laws by examining their effects specifically on youth violence and intimate partner violence. This study has four specific aims. Aim 1 will estimate the impact of PTP laws on youth homicide, suicide, and nonfatal shootings. Data will include death certificates from the National Center for Health Statistics and National Incident-Based Reporting System (NIBRS). Aim 2 will estimate the impact of PTP laws on the perpetration of violent crime and weapons offenses by youth. Data will include the FBI's Uniform Crime Report arrest files and NIBRS. Aim 3 will estimate the impact of PTP laws on the types of firearms used in youth suicide by assessing whether there is a substitution to long guns compared to handguns. Data includes the National Violent Death Reporting System (NVDRS). Aim 4 will estimate the impact of PTP laws on intimate partner homicide and familicide. Data will include Supplemental Homicide Reports (SHR) and NVDRS. Data for each aim will be stratified by firearm involvement, race/ethnicity, and age group (<18 and > 18) where appropriate to assess for differential impacts across subgroups. We propose using comparative interrupted time series (Aims 1-4), synthetic control modeling (SCM) (Aims 1-4), augmented SCM (Aims 1-4), and cross- sectional analyses (Aims 3 and 4) to assess the impact of PTP laws on violent outcomes. Our models will control for state-level demographics, socioeconomic correlates of violence and suicide, and other policies previously found to be associated with the outcomes of interest. Utilizing multiple sources of data with both fatal and nonfatal outcomes increases our ability to address each aim and strengthens our ability to make strong causal inferences. This proposed study fills important gaps in our knowledge on effective policies to prevent multiple forms of violence. This proposal is the first to specifically examine the impact of PTP laws on youth violence-related outcomes and only the second examining intimate partner violence. Currently, only 9 states have PTP laws that cover all handgun transfers. Findings from this study could inform how both states and ...