Assessment of Individual-Level Studies
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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.