We observed different patterns of male unintentional and intentional firearm deaths during the four decades from 1969 to 2009, with a great reduction in risk levels from the end of the 1980s, especially of firearm suicide. In fact, male accidental firearm death rates declined during the entire period to a level between one and null per 1 million. We tested whether these encouraging observations might be due to stricter firearms legislation. Our findings did not provide much statistical support to this hypothesis. Given that data about firearm type were not available until 1996 and later—and that those data did not differentiate between rifles, shotguns, and army firearms—the most we can say is that there was evidence of a decrease in estimated trends in male firearm suicide (in the total sample, and in ages 15–34 years old) after 1990, and in male firearm homicide after 2003, which may be related to two laws (no change or increased rates in the reference group). However, other factors than stricter firearms legislation may be related to the changes in suicide rates in males and that these factors had an overall effect on the occurrence of suicide by all methods. Such factors might include prevention strategies, efforts to improve mental health services, and the chain of care for patients with intentional self-harm. In fact, a general reduction in suicide rates by approximately 25% was observed in Norway from 1988 to 1994, i.e.
, before the suicide prevention plans were implemented starting in 1994 [27
]. From 1994 to 2009, during a period when the prevention plans were active, male non-firearm suicide rates did not change significantly (, ). Mental and behavioral disorders, as well as history of intentional self-harm (including suicide attempts), are strong risk factors for suicide [33
]; thus, improved mental health care (both inpatient and outpatient hospital care), and follow-up care for patients who have been treated for intentional self-harm, may in all likelihood prevent suicide. After 1990, and especially during the years from 1998–2006, resources in mental health services increased in Norway. However, this change was not significantly related to either male or female suicide mortality [34
]. Chain of care for patients who have received emergency medical treatment for intentional self-harm is another factor that may be related to change in suicide rates. However, no differences in changes of suicide rates were observed when Norwegian population areas with and without chain of care intervention were compared [35
]. These findings may reflect the complexity and multiplicity in factors that contribute to the occurrence of suicide [36
]. Our observational study was unable to separate any possible effect of firearms legislation from the effects of other factors; thus, we cannot rule out that the firearms laws had no effect on firearm suicide among young males.
Other authors have also reported a decrease in firearm suicide among young males after stricter firearm regulations, as we observed after 1990 (shotgun regulation). Gagné et al
] reported from Quebec, some years after the implementation of Bill C-17 in 1991 to require safe firearm storage, the pace of the decline in firearm suicide rates was twice as great among men aged 15–34 years as among men 35–64 years. Total suicide rates also declined in these two age groups, and Gagné et al
] conclude that among young men “restricting access to firearms in this age group might be effective in reducing suicides”. There are questions about substitution. A previous study by Caron et al
] analyzed the impact of the same law, also in Quebec, and found support for the substitution hypothesis: firearm suicide was replaced by hanging among males. McPhedran and Baker [38
] tested the impact of a cost-intensive 1996 reform on suicide among young people in Australia; more than 600,000 firearms were bought back from private owners and destroyed by the police [17
]. The authors found no evidence that the law had any impact on the 15–34 age group, and suggest that “these findings contribute to the growing body of evidence documenting the limitations of various forms of method restriction as a means of addressing youth suicide” [38
Different hypotheses have been presented regarding firearm restrictions and suicide [3
]. One hypothesis states that removing or controlling access to means of suicide is an effective prevention strategy at both individual and population levels; this is most likely to be effective when it targets both vulnerable groups and commonly used methods. Another hypothesis states that legislation has more or less no impact, or that alternative methods will be used if restrictions apply to the preferred method (e.g., restricted firearm accessibility), hence the total suicide rate will remain unaffected.
Published literature is inconsistent regarding the effect of means restriction. A review of studies about means restrictions [24
] concluded that the risk of substitution with other methods appears to be small; studies tend to indicate that individuals have a preference for a given means, which limits the likelihood of substituting another method. In contrast, other studies have claimed that method substitution does occur [3
]. De Leo et al
] concluded that an observed increase in suicide by hanging in Australia, which happened as suicide by firearm decreased, could not be explained by method substitution alone. The authors suggested that the shift from firearms to hanging could be explained by a combination of gun control legislation and changes in the social acceptability of particular methods of committing suicide.
Regarding homicides, we observed a significant impact on firearm homicide risk after the governmental removal of National Guard weapons stored in private homes. It is assumed that this only affected the group impacted by the legislative change. However, there is no data available to explore this assumption. Associated to specific impact on military personal, Lubin et al
] reported that suicide due to firearms declined significantly after a policy change in the Israeli Defense Forces in 2006, which dictated that soldiers must leave their weapons on base when they go home for weekend leave. There are however, more studies that failed to demonstrate measurable effect of legislation on homicide by firearm, as in a recent study from Canada: This study examined firearm homicides at national level from 1947 to 2008, and relatively few effects of the legislative changes were observed [42
In contrast to findings from other Nordic countries [15
], we did not observe any effect of the 1986 regulation (mandatory examination of hunters) on unintentional firearm deaths. Any potential effect was overridden by a notable and steady reduction in the number of deaths from 1969 on. This reduction goes back to the 1950s [43
], when the mortality rate attributed to unintentional firearms and explosive materials was as much as 30–40 times higher than the risk level observed at the end of our study period. Additionally, our failure to discern an effect of the 1986 regulation may be due to the method we used (the period used to measure the effect of the intervention in the piecewise regression only covered data from 1986 to the implementation of the next law in 1990, ). Moreover, we observed a low incidence of accidental firearm deaths. Also of note, our data set covered all accidental firearm deaths, not only hunting-related fatalities. Studies in the United States and Sweden suggest that between 30% and 50% of all unintentional firearm fatalities are related to hunting [2
]. More detailed studies of both firearm homicides and accidental firearm deaths in larger countries might assist in evaluating the effects of the laws.
Lack of specificity in the classification system of ICD-10 compared with ICD-9 limits the possibility of obtaining important information about firearm type [44
]. In our study, the data available from 1996 was classified by ICD-10. The fact that close to one-half of firearm deaths were coded as caused by “other and unspecified firearm” makes it even harder to determine whether handguns were used less than other types of firearms, as our results suggest. Missing information about firearm type in official mortality data has also been reported in other countries, including the United States [45
]. In the United States, another information system for violent and firearm-related deaths is available, and a study of suicides among youths (<18 years of age) showed that the deceased were nearly as likely to use a long gun as a handgun [46
A number of limitations should be considered when interpreting findings from our study. In public health policy, legal regulation is used as a means to control the environment and improve safety and health, such as reducing fatal firearm injuries [14
]. However, assessing and quantifying a possible impact of a new law is a challenge, e.g., how to measure impact of the legislation for mandatory training for hunters in Norway after 1986. So, the design of our study has limitations, one is that the definition of the period lengths used in the piecewise regression cover very different numbers of years (some a decade, other three years). Further, not all laws have an implementation date of 1 January so some annual figures cover both pre and post legislation. Another limitation is that even if the laws were effective to reduce firearms mortality, each of the laws may have a small impact on the overall number of firearm deaths in the long-term, and a gradual impact over time. This fact combined with the small number of deaths, particularly in the category of accidental firearm deaths, may increase the risk of type II error [48
]. However, the caution about sample size is unlikely to apply to firearm suicides, as the sample size for this category was quite large. Another common problem in such “naturalistic experiments” is that we cannot isolate the effect of a single intervention from effect of other factors, and there are probably confounding social factors that affected the pre-legislation and post-legislation periods.
During the last few decades, the increasing focus on safety and injury prevention together with a change in the public’s behavior and attitudes may have reduced fatal firearm injuries. Legal interventions are only one of many factors associated with such a change in safety culture. So, other factors may have played a role, e.g., such as switching the hunter’s goal from providing food to recreation, adventure and safety.
The method we used to measure the impact of the four firearm laws, with a few years between each implemented law, can “hide” effects. Regression coefficients that were not significant are not necessarily unimportant, but may reflect small sample sizes. Regarding quality of data, misclassification of the external cause of injury may be a problem (e.g., for unintentional firearm deaths) [49
]. As classification of the external cause of firearm deaths may have changed over time, we included all firearm deaths in this study, independent of intent. However, a number of firearm injury deaths may be missing because of an increased number of deaths registered without cause-of-death information since the late 1990s [27
]. Additionally, in other countries such as Australia, there is concern about the deteriorating quality of official suicide mortality statistics [50
], and one consequence is that the impact of firearm laws in public health strategies must be re-evaluated based on more reliable data [55