(CNN) — Proponents of stricter gun laws have another headline to bolster their efforts: Access to firearms in the home increases the risk of violent death.
Researchers at the University of California, San Francisco, in a review of previous studies published Monday, found strong evidence for increased odds of suicide and moderate evidence for increased odds of homicide victimization among people who keep guns at home.
Firearm ownership is more common in the United States (upwards of one-third of households) than in any other country – and firearms cause more than 31,000 deaths a year here, according to the review. Further, the annual rate of suicide by firearms in America is higher than in any other country with reported data; the annual rate of firearm-related homicides in America is the highest among high-income countries.
People who completed suicide – as well as homicide victims – were most commonly men. Most people who completed suicide were white. Most homicide victims were non-Hispanic black or another race.
“Specific characteristics about storage and types of firearms seem to increase suicide risk,” writes Andrew Anglemyer, who authored the review of 15 previous studies in the journal Annals of Internal Medicine. “Firearms that are stored loaded or unlocked are more likely to be used than those that are unloaded or locked, and adolescent suicide victims often use an unlocked firearm in the home.”
Anglemyer and his team go on to note that “the availability of firearms in the home may not be the catalyst for suicidal ideation, but firearms may be a preferred method of suicide among those who have suicidal thoughts.”
They cite 2011 research that showed adolescents with firearm access were no more likely to have suicidal thoughts or a suicide plan in the past 12 months than those without firearm access. However, among adolescents with a suicide plan, those with a firearm in the home were more than seven times more likely to have a plan involving firearms than those without a firearm in the home.
“The evidence that a gun in the home increases the risk for suicide is overwhelming,” writes David Hemenway of the Harvard School of Public Health, in an accompanying editorial, “even stronger than Anglemyer and colleagues’ robust findings.”
One reason for this, he explains, is that the UCSF team examined only individual-level studies. “Anglemyer and colleagues display an opposite and potentially equally misleading bias by excluding population-level evidence (an analysis of a population rather than an individual),” says Hemenway.
Results from ecological studies suggest that state restrictions on firearm ownership are associated with decreases in firearm-related suicides and homicides.
Since 1996, federal law has prohibited U.S. Department of Health and Human Services agencies from using funds for research that could be interpreted as promoting or advocating for gun control.
“Although there is little evidence that having a gun reduces the risk for homicide victimization,” writes Hemenway, “there is not yet compelling evidence that having a gun substantially increases the risk for homicide victimization for most men. What does put men at substantially increased risk for homicide victimization is other men having access to guns.”
For most families, bringing a gun into the home substantially increases the risk for suicide for all family members and the risk for women being murdered in the home, according to the study.
“Evidence not included in their review also indicates that gun in the home increases the risk for homicide victimization for others in society. This increased risk may be due to someone in the family shooting others (for example, the Sandy Hook Elementary school shooting) or the gun being stolen and used by criminals,” Hemenway writes. “Obtaining a firearm not only endangers those living in the home but also imposes substantial costs on the community.”