for the purpose of suicide, and both studies concern the purchase of handguns in states with gun registration laws, so they do not indicate how many guns might be purchased for the purpose of suicide if gun registration did not occur. The most important limitation is that these studies do not indicate whether handgun purchasers would have substituted other methods of suicide if a gun were not available, and do not measure other factors, such as history of substance abuse, psychiatric illness, criminal activity, or domestic violence, which might explain or modify a link between gun ownership and propensity for suicide.

Assessment of Individual-Level Studies

All of the individual-level studies reviewed here have found a strong association between gun access and the likelihood that a suicide, if it occurs, will take place by means of a gun. There is also strong evidence that some guns are specifically purchased for the purpose of suicide, suggesting that some individuals definitely prefer a firearm to commit suicide, if suicide is their intention. But such reverse causality does not entirely explain the link between gun access and overall risk of suicide, because several studies have found that adolescents (who are not eligible to purchase guns) are at higher risk of suicide if they live in a home with a gun.

It is not yet clear if the individuals who used a gun to commit suicide would have committed suicide by another method if a gun had not been available. Overall, the U.S. studies have consistently found that household gun ownership is associated with a higher overall risk of suicide, but the estimate of such an association was significantly smaller in a study from New Zealand. Although reverse causality cannot explain the association between guns and risk of suicide for adolescents, it remains possible that some other heritable or environmental family trait links the likelihood of gun ownership and suicide. For example, several studies have found that adolescents with access to firearms in their homes are also more likely to report thoughts of suicide, suggesting that it may be some unobserved characteristic of gun-owning families in the United States that places such adolescents at higher risk.

Next Steps

Despite these concerns with the existing literature, it is the committee’s view that individual level studies in general, and case-control studies in particular, have been underutilized in this literature. All empirical research in this area must be cognizant of the potential for substitution and confounders, but individual-level study designs allow researchers to avoid the biases introduced by aggregation and proxy measures of ownership and are

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