On the 19-year anniversary of the Columbine school shooting, the US honors the National Day of Action to Prevent Gun Violence in Schools today (April 20). Debating the best way to control gun violence in the US often seems like a daunting exercise. But social science research points to a simple truth: The more obstacles people face in attempting to harm themselves or others, the more likely they are to give up.

In 1963, Britain experienced 5,714 suicides. Over the next several years, that number declined steadily and quickly; by 1975, the country had 3,693 suicides. This decline took place against a rise in suicides throughout the rest of Europe.

Social scientists started looking for something to explain the drop. What they realized was that the decrease in suicide had coincided with the progressive transition in British households from carbon monoxide-producing coal gas to natural gas, beginning in 1958.

Prior to the switch, 40% of all suicides in Britain were suicides by household gas, a death that was relatively easy, painless, and required little planning. People would just turn the oven on and drift away. When that option was no longer available, fewer people chose to commit suicide overall.

This phenomenon was documented by criminologists Ronald V. Clarke and Patricia Mayhew in a 1988 study titled “The British Gas Suicide Story and Its Criminological Implications.” Clarke and Mayhew found that, when denied the most convenient means of being able to kill themselves, many people just didn’t bother. “Few of those prevented from using gas appear to have found some other way of killing themselves,” they write in their abstract. “These findings suggest that suicide is an intentional act designed to bring an end to deep, though sometimes transient, despair, chosen when moral restraints against the behavior are weakened, and when the person has ready access to a means of death that is neither too difficult nor repugnant.”

Furthering the hypothesis that suicidal feelings are often transient, a 1978 study found that out of 515 people who were stopped by someone from jumping off the Golden Gate Bridge, only 10% went on to commit suicide by other means. Suicide barriers, in areas where there are not other easily accessible places to jump from, have been shown to reduce suicide by jumping in those areas. The more obstacles we put in front of someone looking to do something so drastic, the more time we give for those feelings to pass.

“Means reduction” could be key to understanding how to stop an epidemic of school shootings in the US.

This phenomenon is called “means reduction,” and whether it’s done by accident or on purpose, studies have shown that it’s one of the most effective ways of preventing suicide. It could also be key to understanding how to stop an epidemic of school shootings in the US.

Opponents of gun control often argue that if we take guns away, those intent on killing or committing crimes with them will simply “find another way.” They’ll use knives and go on a mass stabbing. Or perhaps they’ll turn to bombs or stones or fire. In social science, this is called “displacement.” While it may be true for those who are especially motivated, studies have shown that when the least convenient means of committing a crime is eliminated, criminals are not more likely to simply turn to another method.

Another Clarke and Mayhew study, for example, found that thefts of motorcycles dropped as much as 60% in Germany after a law was implemented requiring motorcyclists to wear helmets. Because these thefts tended to be crimes of opportunity rather than planned heists, potential thieves were dissuaded from stealing motorcycles due to the increased likelihood of getting caught if they were pulled over for not wearing a helmet. There was not, however, a corresponding rise in thefts of bicycles or cars, likely because neither of those options provided the low risk and high financial reward of stealing motorcycles.

Gun violence and motorcycle theft aren’t the same scenario, to be clear, but the principle of means reduction can be equally applied. What do we have to lose by putting obstacles in place that make it harder for people to act on violent feelings that are potentially transitory? Every second we give someone to turn back, to change their mind, is precious.

What do we have to lose by putting obstacles in place that make it harder for people to act on violent feelings that are potentially transitory?

School shootings tend to be suicidal events. The majority of rampage shooters do not intend to get away with their crimes or come out of them alive; many end up killing themselves or committing “suicide by cop.” And guns are likely to continue to be the weapon of choice for “lone-wolf” killers, given that they remain the most convenient means of committing a mass murder, and that there are more legal restrictions on purchasing explosive materials than there are restrictions on gun-buying.

What having access to a gun does is put the option on the table in a way that nothing else does. It plants a seed that might not otherwise have anywhere to germinate.

In other situations involving guns, ease of access has had a direct impact. When a gun is present in a domestic violence situation, a woman is 500% more likely to be murdered. Areas with lower rates of gun ownership have lower overall homicide rates than areas with higher rates of gun ownership. Although women are more likely to contemplate suicide and attempt suicide, suicide attempts by men are more likely to be successful, in part because they are more likely to use firearms. The methods favored by women tend to be the options that give them more of a chance to back out. Suicide rates are higher in rural areas for this same reason. And women who live in states that require private sellers to conduct background checks are 38% less likely to be shot and killed by a domestic partner. Living in a home with a gun increases the likelihood that those in it will be victims of suicide or homicide.

What we know about people tells us that simply having access to guns makes it more likely that they will kill themselves, and others.

At the end of the day, the massacres that are happening in American schools are simply not happening in countries with stricter gun control laws. After a mass shooting that led to the deaths of 35 people in Australia in 1996, the country enacted stricter gun control and initiated a major gun buyback program. They have only had one school shooting since, and zero school mass knifings or bombings.

The NRA loves to say “guns don’t kill people, people kill people.” That’s not untrue. But what we know about people tells us that simply having access to guns makes it more likely that they will kill themselves, and others.

Means reduction works. If we know that people who are suicidal don’t always “find another way” when the easiest and most lethal form of doing that is unavailable to them, it stands to reason that they will not always “find another way” when it comes to homicide. Reducing access to guns can have a meaningful impact on the number of mass killings traumatizing our schools today.

We welcome your comments at ideas@qz.com.

Correction: An earlier version of this article incorrectly referred to a mass shooting in Australia as a school shooting.