The relationship between gun prevalence and suicide is stronger than the relationship between guns and homicide, as the Harvard Injury Control Research Center’s Means Matter project shows. People who die from suicide are likelier to live in homes with guns than people who merely attempted suicide, and states with higher rates of gun ownership have higher rates of gun suicide.
This isn’t proof of causality, but many of the complicating factors that would disprove a causal relationship — say, the possibility that people in rural areas are both likelier to own guns and likelier to be depressed — don’t check out; depression actually isn’t higher in rural areas, for example. And the causal mechanism by which guns would increase suicide rates is plausible. Studies suggest that suicide attempts using guns are fatal in the vast majority of cases, while attempts using cuts or poisoning are only fatal 6 to 7 percent of the time.
Furthermore, there’s evidence that gun control can reduce suicide rates. A buyback program that wound up taking a fifth of Australia’s guns off the street wound up reducing firearm suicides by 74 percent without affecting non-firearm suicides. When the Israeli Defense Forces stopped letting soldiers bring their guns home over the weekend, suicides fell 40 percent, primarily due to a drop in firearm suicides committed on weekends. Firearm suicides are less common in US states that check if potential gun purchasers are mentally ill or criminal fugitives.