All SHP News News April 4, 2022

Californians Living with Handgun Owners Twice as Likely to Die by Homicide

In the largest cohort study of its kind, research led by SHP's David Studdert and Yifan Zhang shows that people living with handgun owners are significantly more likely to die by homicide compared with neighbors in gun-free homes.
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Americans purchased firearms at a record-breaking rate during the COVID-19 pandemic.  Surveys consistently show that gun buyers’ main motivation is to protect themselves and their families. New Stanford-led research casts doubt on these perceived safety benefits. 

In a massive cohort study that examined firearm purchases and deaths among nearly 18 million Californians over 12 years, the researchers found that people living with handgun owners were more than twice as likely to die by homicide, compared with their near neighbors living in gun-free homes. Fatal shootings at the hands of spouses or intimate partners were seven times more common among people living with handgun owners — and 84% of those victims were women.

The study, published in the Annals of Internal Medicine, adds to a growing body of evidence showing that a gun in the home is associated with higher risks of injury and death.

In an accompanying editorial, Christine Laine, the journal’s editor in chief, and Sue Bornstein, chair-elect of the American College of Physicians’ Board of Regents, write: “That firearm-related injury has surpassed motor vehicle injury as a cause of years of life lost in the United States is striking proof that firearm-related injury is a significant public health problem.”

They argue that gun violence both inside and outside the home should be treated as an epidemic and tackled with a multifaceted approach.

“Despite widespread perceptions that a gun in the home confers security benefits, nearly every credible study to date suggest that people who live in homes with guns are at higher—not lower—risk of dying by homicide,” said lead author David Studdert, LLB, ScD, a professor of health policy in the School of Medicine’s Department of Health Policy, and a professor of law at Stanford Law. “But homes don’t own guns, people do, and it’s important to sort out exactly who faces elevated risks in homes with guns, and how large those risks are. There’s an analogy to tobacco here: we think about risks from secondhand smoke differently than the risks smokers themselves face by choosing to smoke.”

We were particularly interested in homicides occurring in or around the home because protecting one’s home is a major motivation for gun ownership and a plurality of homicides occur in the home.
David Studdert
Professor of Health Policy, Professor of Law

Only one previous study has quantified the risks faced by individuals who do not own guns but live with others who do. It was conducted 25 years ago and examined too few deaths to reach clear conclusions.

The research team followed 17.6 million California residents aged 21 and older. Everyone in the study sample was living with at least one other adult in a handgun free home at the beginning of the study in October 2004.  Over the next 12 years, 600,000 of them began living with handgun owners, usually because someone in their household purchased one.

“Our goal was to estimate the effect of household exposure to handguns on nonowners’ risk for dying by homicide,” they wrote. “We were particularly interested in homicides occurring in or around the home because protecting one’s home is a major motivation for gun ownership and a plurality of homicides occur in the home.”

Nationwide, most of the people who don’t own guns and live with gun owners are women.

“Two-thirds of our study population were women,” said Yifan Zhang, PhD, a Research Scholar in the Department of Health Policy and study co-author. “It’s important to recognize that women bore the brunt of the elevated risks we identified. And the fatal assaults they experienced often took the form of being shot by men they lived with.”

The researchers did not detect evidence that people living in homes with guns had lower risks of being killed by strangers. On the contrary, risks of such deaths trended higher too, although the result was not statistically significant.

An earlier study by the research team using the same cohort found that men who personally own handguns were eight times more likely to die of gun suicides than men who don’t own handguns — and female owners were 35 times more likely to die this way than females nonowners.

“The evidence that ready access to firearms leads to higher rates of suicide is overwhelming,” said Matthew Miller, MD, ScD, a professor of epidemiology at Northeastern University and senior author of the study. “Our study shows the risk of fatal assault in homes with guns is higher too. In other words, there’s no homicide benefit to counterbalance the suicide risk that occurs when someone brings a gun into a household. Just the opposite. Gun owners’ family members bear a lot of that risk.”

The other co-authors of the study were Erin E. Holsinger, MD; Lea Prince, PhD; Alexander F. Holsinger, BA; Jonathan A. Rodden, PhD; and Garen J. Wintemute, MD, MPH.

The study was funded by the National Collaborative on Gun Violence Research.  The Fund for a Safer Future, the Joyce Foundation, Stanford Law School, and the Stanford University School of Medicine supported assembly of the cohort used in the study.

David Studdert

Professor of Health Policy, Professor of Law
Focuses on impact of legal system on health and well-being of populations
David Studdert

Yifan Zhang

Research Scholar
Applies statistical analysis methods in health policy research
Yifan Zhang

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