Millions of Americans may have asked themselves these questions, or versions of them—especially in the wake of horrific mass shootings like those in Buffalo and Uvalde. Record-breaking spikes in gun sales over the last two years, alongside surveys indicating that self-protection continues to be the dominant reason for buying guns, underscore a widely-held belief that a gun in the home has security benefits.

A new study from my research team, recently published in the Annals of Internal Medicine, shows no such benefits. We found the opposite: people living in homes with guns face substantially higher risks of being fatally assaulted.

We studied 18 million adults living in California. Nearly 2,300 of them died by homicide over the 12 years of the study. Thanks to California’s historical archive of firearm transactions, we could identify who in this enormous population personally owned guns, and who lived with gun owners. The study’s goal was to see whether homicides were more or less likely to occur in homes with handguns.