摘要：Objectives. To investigate the impact of the Australian National Firearms Agreement (NFA) on suicide and assault mortality. Methods. We conducted a retrospective cross-sectional difference-in-difference study of the impact of the NFA on national mortality rates in the Australian population from 1961 to 2015. Results. The NFA had no additional statistically observable impact on firearm-related suicides in women ( P = .09) and was associated with a statistically significant increase in the trend in men ( P < .001). Trends in non–firearm-related suicide deaths declined by 4.4% per year (95% confidence interval [CI] = 4.1%, 4.8%) in men after the introduction of the NFA and increased in women by 0.3% (95% CI = 0.1%, 0.7%). Trends in non–firearm-related homicides declined by 2.2% per year (95% CI = 1.5, 3.8%) in women and 2.9% per year (95% CI = 2.0%, 3.7%) in men after the introduction of the NFA, with a statistically significant improvement in trends for women ( P = .04) but not for men ( P = .80). Conclusions. The NFA had no statistically observable additional impact on suicide or assault mortality attributable to firearms in Australia. Firearm-related mortality remains a significant public health problem in the United States. More than 30 000 people die every year from a firearm-related injury, primarily because of suicide, 1 and firearm mortality rates in the United States are orders of magnitude higher than are those in other high-income countries. 2 Laws restricting gun access are known to reduce firearm-related mortality 3 but remain limited in the United States. 4 Mass shootings are a subset of firearm-related homicide that, although only a tiny proportion of the total burden of firearms-related mortality and hospitalization, 5 attract greater media attention and public alarm, and gun control efforts are often revived in their wake. Laws to prevent mass shootings are seen as more politically palatable than broader laws targeting all forms of firearm-related mortality, but their effectiveness in the United States has not been confirmed. 6 Public health experts have recently added urgency to calls for action on both mass shootings and broader firearm-related mortality, 7 but after 2 decades of restrictions on research into the cause of gun violence in the United States, 8 the national debate depends heavily on evidence from successful policy enacted overseas. In this context, the Australian National Firearms Agreement (NFA) is often presented as a model for a minimal set of firearms laws for the United States. 9 This agreement restricted access to some classes of firearms, regularized and tightened state-level licensing laws, and introduced a gun buyback scheme and amnesty that led to the recall of approximately 640 000 guns. 10 Although it was designed to prevent mass shootings and may have been effective in this goal, 11 some researchers have claimed that the NFA also had a quantifiable impact on firearms-related suicide and homicide. A 2010 study found an 80% reduction in suicide mortality attributable to the NFA 12 but failed to adjust for the long-standing declining trend in firearm-related mortality and used ordinary least squares regression, limiting the validity of its findings. The most recent study, published in 2016, found that firearm-related suicides and homicides declined more rapidly after the introduction of the NFA and concluded that the NFA was particularly effective against gun-related suicide deaths. 13 This study did not provide a comprehensive statistical analysis of mortality, however, and suffered from a significant flaw that may have led to misleading results: it did not compare the impact of the NFA on intentional gun-related deaths after adjusting for changes in nonfirearm mortality that occurred in the same period. One 2006 study considered the possibility that there was a general downward trend in suicide deaths at the time the NFA was introduced but did not compare trends statistically and had only limited post-NFA data on which to make this comparison. 14 We analyzed changes in trends and levels of intentional firearms-related mortality in Australia. On the basis of the assumption that nonfirearm deaths were unaffected by the NFA, we reassessed the impact of the NFA using a difference-in-difference (DiD) approach and treated nonfirearm deaths as a control group to obtain a more accurate, scientifically robust estimate of the impact of the NFA on intentional firearm-related deaths in Australia.
