What is already known on this topic

Gun control is a highly topical yet polarising political issue.1 To date, there is limited evidence on the impact of gun law reforms on firearm-related violence and suicide.2 In Australia, substantial changes in gun laws that significantly restrict the use and ownership of weapons were introduced in 1996 following the Port Arthur massacre in Tasmania. In 2006, Chapman et al analysed the 10-year impact of this reform on firearm-related deaths (including suicides)3 and found no subsequent mass shootings and an accelerated decline in firearm deaths, especially suicides, in the decade following the reforms. In this new paper, they update the evidence over a longer period.

Methods of the study

Chapman et al carried out an observational study to explore the impact of gun law reform on the incidence of mass firearm homicides and total firearm deaths in Australia. They collected data from 1979 to 2013 (18 years before and 17 years after the gun reform laws were enacted) on the number of intentional firearm deaths (suicide and homicide) from the Australian Bureau of Statistics mortality database, and calculated intentional firearm death rates per 100 000 population for each year of the study period. They excluded police shootings as these would not have been affected by the gun law reform. Using negative binomial regression analysis, they explored trends in the annual rates of firearm-related deaths in the periods before and after 1996. They examined whether there was a compensatory upward trend (or lesser downward trend) in non-firearm deaths over the same period to evaluate whether other lethal means were used to replace firearms. They also collected data on the incidence of mass fatal shootings (involving five or more victims) over the study period.

What does this paper add

• A significant decline in firearm deaths was observed following the introduction of stringent gun laws in 1996.

• The study confirms and extends previous findings that no mass shootings have taken place in Australia since 1996, whereas 13 such massacres had occurred in the previous 17 years.

• Despite an already downward trend in total firearm deaths in 1979–1996 (average decline of 3% annually), this trend accelerated and in a stepwise manner in the following period (average decline of 4.9% annually). Firearm suicides were the largest component cause of total firearm deaths and a significant accelerated decline in the rate of firearm suicides was also observed following the change in gun laws (ratio of trends 0.981, 95% CI 0.970 to 0.933). A similar reduction in total firearm homicides was seen between the two study periods. A non-significant acceleration in the previous decline in annual homicide rates was also observed following the change in gun laws (ratio of trends 0.975, 95% CI 0.949 to 1.001).

• The data showed no apparent substitution to other lethal methods.

Limitations

• The most notable limitation is that it is not possible to determine a causal link between the change in gun laws and the reduction in firearm deaths, although causation is plausible. Other explanations such as improved trauma care and increased access to emergency treatment are discussed.

• This study is limited to Australia, where there were specific changes in gun ownership legislation which involved the government prohibiting and buying back rapid-fire long guns. It is unclear to what extent the results would be applicable in other jurisdictions where firearm legislation (including ownership, licensing, permit and sales laws) and potential reform would be qualitatively different.

• The study does not investigate the impact on high-risk populations, where it has been argued any such changes will have substantial benefits.2

What next in research

Gun laws and changes in firearm death rates are complex and multifaceted issues that require substantially more research to convince policymakers about any potential benefits of limiting firearm access. Research supporting a causal link between strict gun laws and a reduction in firearm deaths is much needed but difficult to interpret due to the limitations in determining ‘control’ populations. Where legislative changes have already taken place, there are opportunities for ongoing large epidemiological analyses provided robust data on gun ownership and gun-related deaths are maintained. Where changes are being considered, there may be a window of opportunity to carry out prospective case–control studies which would assist in confirming causation.

Do these results change your practices and why?

In countries where gun reform is under consideration, most notably the USA, findings from this study are relevant to a growing body of evidence on the beneficial impact of limiting firearm access on reducing mass shootings, homicides and suicides. The study also serves as a reminder that suicide and homicide rates can be reduced by restricting lethal methods, and inquiries into the accessibility of weapons and other harmful means should be routine when assessing individuals at risk of suicide and self-harm.