A study estimates that the 3 million guns sold in the several months after Sandy Hook caused about 60 more accidental gun deaths than would have occurred otherwise.

The study, published in the journal Science, was done by twp Wellesley College economists.

Using the number of background checks as their proxy, they found an increase in gun sales in the four months afterward Sandy Hook. 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 analysis found that greater exposure to guns may plausibly increase the risk of accidents. In addition, it found that gun exposure may increase if new guns are purchased or previously owned guns are removed from storage.  The researchers attribute many of the deaths to improper or inadequate gun storage.

Yet, the researchers say, "We caution against interpreting our results as representing a direct link between the greater gun sales and these additional deaths. Gun sales represent a proxy for gun exposure in our analysis; they are correlated with an increased interest in firearms, even among current gun owners, as shown in our Google Trends analysis. We cannot determine the extent to which the impact is driven by sales or greater exposure to existing guns."

However, taken as a whole the researchers say "Our analysis provides evidence indicating that the spike in gun exposure that followed the Sandy Hook school shooting increased the incidence of accidental firearm deaths, particularly among children. Our findings support the recommendations of the American College of Preventive Medicine, which include safe gun-storage laws and physician counseling of their patients about approaches that can help reduce deaths associated with the accidental discharge of a firearm."

http://science.sciencemag.org/content/358/6368/1324.full