RESEARCH RECOMMENDATIONS
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Firearms, Criminal Violence, and Suicide
Despite the richness of descriptive information on the associations between
firearms and violence at the aggregate level, explaining a violent
death is a difficult business. Personal temperament, the availability of weapons,
human motivation, law enforcement policies, and accidental circumstances
all play a role in leading one person but not another to inflict
serious violence or commit suicide.
Because of current data limitations, researchers have relied primarily
on two different methodologies. First, some studies have used case-control
methods, which match a sample of cases, namely victims of homicide or
suicide, to a sample of controls with similar characteristics but who were
not affected by violence. Second, some “ecological” studies compare homicide
or suicide rates in large geographic areas, such as counties, states, or
countries, using existing measures of ownership.
Case-control studies show that violence is positively associated with
firearms ownership, but they have not determined whether these associations
reflect causal mechanisms. Two main problems hinder inference on
these questions. First and foremost, these studies fail to address the primary
inferential problems that arise because ownership is not a random decision.
For example, suicidal persons may, in the absence of a firearm, use other
means of committing suicide. Homicide victims may possess firearms precisely
because they are likely to be victimized. Second, reporting errors
regarding firearms ownership may systemically bias the results of estimated
associations between ownership and violence.
Ecological studies currently provide contradictory evidence on violence
and firearms ownership. For example, in the United States, suicide appears
to be positively associated with rates of firearms ownership, but homicide is
not. In contrast, in comparisons among countries, the association between
rates of suicide and gun ownership is nonexistent or very weak but there is a
substantial association between gun ownership and homicide. These crosscountry
comparisons reflect the fact that the suicide rate in the United States
ranks toward the middle of industrialized countries, whereas the U.S. homicide
rate is much higher than in all other developed countries.
The committee cannot determine whether these associations demonstrate
causal relationships. There are three key problems. First, as noted above,
these studies do not adequately address the problem of self-selection. Second,
these studies must rely on proxy measures of ownership that are certain to
create biases of unknown magnitude and direction. Third, because the ecological
correlations are at a higher geographic level of aggregation, there is no
way of knowing whether the homicides or suicides occurred in the same areas
in which the firearms are owned.
In summary, the committee concludes that existing research studies and
data include a wealth of descriptive information on homicide, suicide, and
firearms, but, because of the limitations of existing data and methods, do not
credibly demonstrate a causal relationship between the ownership of firearms
and the causes or prevention of criminal violence or suicide. The issue of
substitution (of the means of committing homicide or suicide) has been almost
entirely ignored in the literature. What sort of data and what sort of
studies and improved models would be needed in order to advance understanding
of the association between firearms and suicide? Although some
knowledge may be gained from further ecological studies, the most important
priority appears to the committee to be individual-level studies of the association
between gun ownership and violence. Currently, no national surveys on
ownership designed to examine the relationship exist. The committee recommends
support of further individual-level studies of the link between firearms
and both lethal and nonlethal suicidal behavior.
Deterrence and Defense
Although a large body of research has focused on the effects of firearms
on injury, crime, and suicide, far less attention has been devoted to understanding
the defensive and deterrent effects of firearms. Firearms are used by
the public to defend against crime. Ultimately, it is an empirical question
whether defensive gun use and concealed weapons laws generate net social
benefits or net social costs.