In the days after the horrific shooting at Sandy Hook Elementary School, gun enthusiasts rushed to buy millions of firearms, driven by fears that the massacre would spark new gun legislation. Those restrictions never became a reality, but a new study concludes that all the additional guns caused a significant jump in accidental firearm deaths.

The study, published Thursday in the journal Science, estimates that the 3 million guns sold in the several months after Sandy Hook caused 60 more accidental gun deaths than would have occurred otherwise. Children were killed in a third of them.

The work by two Wellesley College economists tackles one of the biggest questions in gun research: how to measure the relationship between gun prevalence and gun deaths. For decades, hamstrung by lack of funding and the politically charged landscape surrounding gun control, researchers have lacked data to try to answer that question.

With no federal or state databases of gun ownership to work from, for example, researchers have struggled to definitively correlate deaths to the presence of guns in homes. They have grappled with what conditions would best determine the factors – gun sales, different state laws, the type of guns available – that might affect gun violence and death.

By seizing on the surge of firearm purchases after the 2012 tragedy in Newtown, Conn., the Wellesley team essentially set up an experimental model to study what happens after such a sudden increase in gun sales.

Neither of the two statisticians who conducted the research – Phillip Levine and Robin McKnight – had worked on gun violence before. McKnight had mostly looked at health insurance issues, and Levine at such social policies as teen pregnancy. They launched their study after seeing a chart in a newspaper showing the sharp upturn in gun sales after Sandy Hook. “It brought up so many questions,” Levine said.

The two scrutinized weekly search data from Google, which showed that terms like “buy a gun” increased fourfold as President Barack Obama began pushing for new gun restrictions.

Using the number of background checks as their proxy, they found an increase in gun sales in the four months afterward. They then compared that number to two databases of deaths nationwide, which showed a 27 percent increase in accidental gun deaths for all ages and a 64 percent increase among children during that period.

The researchers attribute many of the deaths to improper or inadequate gun storage.

“It also shows the unintended consequences of public policy,” said Levine, noting that it wasn’t the shooting itself that caused an increase in gun sales and deaths but the political debate over potential legislation. “It suggests that in pursuing stronger restrictions, we have to consider the likelihood of actual legislation getting passed. Because if it fails, there are short-term costs.”

While the study is garnering interest and praise for its novel approach, longtime gun researchers point to a major hole in the findings. The study found that accidental gun deaths increased, but the surge in gun sales had almost no effect on homicides and suicides that were intentionally committed – and that make up the lion’s share of gun deaths in America.

“It’s a serious and provocative study, but it’s important to keep in mind that in the grand scheme of things, accidental deaths are relatively rare,” said David M. Studdert, a professor at Stanford Law School. “Suicides and homicides, that’s the main game that researchers are trying to figure out when it comes to the causal relationships between guns and mortality.”

“It’s a novel approach, and it will spark a lot of discussion and additional work, which is much needed. But I don’t think this will be the final word,” said Philip Cook, a leading gun policy expert at Duke University.

One nagging question in the new study, Cook noted, is that while the spike in gun sales after Sandy Hook was significant, it only added a small amount of guns to the country’s total gun stock. “It’s surprising that such a small increase in the overall gun stock could have such a large effect on one category, accidental deaths, and yet no effect on other categories,” he said.

The study is part of a larger wave of renewed enthusiasm and new approaches being applied to gun research, Cook said. “There’s increased public attention and a sense that this is important, and it creates this snowballing effect. The political intensity around guns [doesn’t] seem to be changing, but I feel hopeful about the future of the research.”