Moe CA, Haviland MJ, Bowen AG, et al. - In this difference-in-differences analysis of a national cohort, researchers ascertained if state laws that raised the minimum age to purchase and/or possess a handgun to 21 years were correlated with lower rates of firearm homicide perpetrated by young adults aged 18 to 20 years. Thirty-five thousand nine hundred sixty firearm homicides were perpetrated by young adults aged 18 to 20 years during the study period. No statistically significant change in homicide rates perpetrated by young adults between the ages of 18 and 20 has been reported in states that have adopted stricter minimum age laws relative to those that have not. Implementation of stricter minimum age laws for firearm purchase or possession has not been correlated with lower rates of firearm homicides perpetrated by young adults; policies limiting access through informal channels may have a greater impact.