By Nanette Asimov
A Stanford University study of homicide rates among millions of Californians offers strong new evidence that people who live with a handgun owner are at far greater risk of dying by homicide than those who don’t.
The 12-year study of 17.6 million California residents, published Monday in the Annals of Internal Medicine, serves as a rebuttal to the popular notion that gun ownership increases safety, researchers said. They found that people who live with a handgun owner are seven times more likely to be shot to death by a spouse or partner — and that 84% of the victims are women.
People who live with a handgun owner are more than twice as likely overall to be killed by a firearm than those in a home with no gun. Two-thirds of those victims are women, the study found.
“It’s important to recognize that women bear the brunt of the elevated risks,” said the study’s co-author Yifan Zhang, a researcher at Stanford Health Policy. “The fatal assaults they experienced often took the form of being shot by men they lived with.”
David Studdert, an expert in health policy and law at Stanford and the study’s lead author, called the findings “pretty shocking.”
“The gun, instead of being protective, is actually the instrument of death,” he said. While most gun buyers report being motivated by a wish for better security, “our findings suggest that by bringing a gun into the home, they’re getting the opposite — the people they live with are at higher risk.”
The study also found no evidence that living with a gun owner protected the non-gun owner from being killed by a stranger.
The research is the first large-scale study to compare homicide risks among people who live with gun owners and people who live in a home without a gun.
The researchers tracked 17.6 million Californians who did not own guns over 12 years, from 2004 through 2016. Nearly 600,000 of those people began living with a handgun owner at some point.
The researchers then looked at homicides among non-gun owners in both groups: those who lived with a gun owner and those who didn’t.
Victims who lived with a handgun owner died by homicide at a rate of 3.7 per 100,000, compared to 2.11 per 100,000 among those who did not.
Victims killed at a home where someone else owned a handgun died at a rate of 2.37 per 100,000, compared to 0.78 per 100,000 among those in a home without the firearm.
Those killed in a home with a handgun were more than four times as likely to die by gunfire than those without a handgun in the home, the study found.
The researchers said they were unable to determine whether the victims were killed by the actual handgun owners. Also, some households characterized as gun-free may actually have had a gun. The researchers said those might have been misclassified if the handgun had been acquired illegally or acquired before 1985.
The researchers said their reliance on handgun data, rather than other kinds of guns, should not affect the findings because handguns are used in about 90% of California homicides.
The study notes that one in three homes in the U.S. has at least one firearm.
The right to “keep and bear arms” is guaranteed under the Constitution. Yet the specifics of regulating gun use and ownership have been among the nation’s most contentious political debates.
Could the stark findings of the Stanford study change the course of the long-running feud?
A spokesperson from the National Rifle Association declined to comment on the findings. But John Lott, a gun-rights activist who served in the Trump administration, was ready to weigh in.
“It’s a stupid study,” Lott told The Chronicle, asserting that the Stanford researchers and the experts who peer-reviewed their work had a lot to learn about how to conduct a proper analysis.
Lott, who did not examine the study because it had not yet been made public, nevertheless said it was poorly done because the authors did not explain why the homes had guns.
“If the gun owner bought the gun because he’s in a higher-risk area than the person who doesn’t own the gun, don’t you think you’re risk of dying is higher?” Lott said, adding that a better study would have compared people living in the same neighborhood.
Studdert, the lead author, said that’s exactly what this study did.
“Our results were based on comparisons between people living the same small neighborhood,” Studdert, noting that the “homicide risk for each person living with a gun owner was compared only with the same risk among people living in homes very nearby.”
Yet the study’s findings, however shocking, won’t settle the debate over gun rights, he said.
Instead, they help “build up a picture of the truth,” Studdert said. They contribute “to the mounting scientific evidence that a gun in the home causes more harm than good.”
The study received funding from the National Collaborative on Gun Violence Research, the Fund for a Safer Future, the Joyce Foundation, and Stanford’s schools of medicine and law.
Nanette Asimov is a San Francisco Chronicle staff writer. Email: nasimov@sfchronicle.com Twitter: @NanetteAsimov