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

particularly well suited to the exploration of “third variables” that could

explain the link between firearms and suicide in the United States.