The Stanford study took advantage of the unusually comprehensive body of information on firearm sales in California. All lawful gun purchases and transfers must be transacted through a licensed firearms dealer, who then relays the information to the state’s Department of Justice, where it is archived. The research team obtained records of all firearm acquisitions dating back to 1985, then linked them to death records.
The researchers found that people who owned handguns had rates of suicide that were nearly four times higher than people living in the same neighborhood who did not own handguns. The elevated risk was driven by higher rates of suicide by firearm. Handgun owners did not have higher rates of suicide by other methods or higher rates of death generally.
The researchers said the very high risk of suicide for female handgun owners, relative to female nonowners, was particularly noteworthy. It has long been known that women attempt suicide more frequently than men but have fewer completed suicides. The standard explanation is that the methods women tend to use are less lethal than those men tend to use. However, the study showed that this is not true for female gun owners.
“Women in our cohort who owned guns and died by suicide usually used a gun,” said Yifan Zhang, PhD, a biostatistician at Stanford Health Policy and co-author of the study. “Handgun ownership may pose an especially high risk of suicide for women because of the pairing of their higher propensity to attempt suicide with access to and familiarity with an extremely lethal method.”
Disentangling Competing Explanations
One major challenge with studies examining the relationship between gun access and suicide risk has been determining whether people who purchase handguns already have plans in place to harm themselves, or whether the presence of a handgun creates new risks.
The unique, longitudinal nature of the Stanford study helped to disentangle these competing explanations.
“There appears to be some of both happening,” said senior author Matthew Miller, professor of health sciences and epidemiology at Northeastern University. “New handgun buyers had extremely high risks of dying by firearm suicide immediately after the purchase. However, more than half of all firearm suicides in this group occurred a year or more later. Consistent with prior work, our findings indicate that gun access poses a substantial and enduring risk.”
Other Stanford co-authors of the study are research analyst Lea Prince, PhD, and research assistant Erin Holsinger, MD — both at Stanford Health Policy; and Jonathan Rodden, PhD, professor of political science.
Researchers at Erasmus University, in the Netherlands, and the University of Melbourne, in Australia, also contributed to the work.
The research was supported by the Fund for a Safer Future and the Joyce Foundation, as well as Stanford Law School and the Stanford University School of Medicine.