RESEARCH RECOMMENDATIONS

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.