The US gun-control debate may have both sides shooting their mouths off, gunning for each other, going off half-cocked, and [insert tiresome idiom here], but a group of biostatisticians and epidemiologists decided to cut through the cant and apply rigorous research to one critical question: does carrying a gun increase your safety?

"On average," the researchers concluded, "guns did not protect those who possessed them from being shot in an assault." The finding was published in an American Journal of Public Health paper entitled, straighforwardly enough, "Investigating the Link Between Gun Possession and Gun Assault".

"Although successful defensive gun uses can and do occur," the report contends, "the findings of this study do not support the perception that such successes are likely."

The researchers, all from the University of Pennsylvania, conducted their study with a stated goal of determining "the possible relationship between being shot in an assault and possession of a gun at the time." To do so, they investigated 3,485 shootings "of all types" in Philadelphia, Pennsylvania, from October 15, 2003, to April 16, 2006.

The researchers then excluded self-inflicted, unintentional, and police-related shootings, plus gun injuries of undetermined intent. They further narrowed their study sample by age – no one under 21 and therefore not able to legally own a gun, for example – and other factors, which reduced the sample to 2,073 shootings. They then randomly selected 677 of those for further study, and paired each of those participants with "population-based control participants." A detailed description of the study's painstaking methodology can be found here.

The resulting data, after suitable massaging, revealed a clear result. "[I]ndividuals in possession of a gun were 4.46 (P < .05) times more likely to be shot in an assault than those not in possession. Among gun assaults where the victim had at least some chance to resist, this adjusted odds ratio increased to 5.45 (P < .05)."

That's the hard numerical analysis. The paper also offers what it characterizes as "a few plausible mechanisms" by which possession of a gun might increase a person's risk of being involved in a gun assault.

A gun may falsely empower its possessor to overreact, instigating and losing otherwise tractable conflicts with similarly armed persons. Along the same lines, individuals who are in possession of a gun may increase their risk of gun assault by entering dangerous environments that they would have normally avoided. Alternatively, an individual may bring a gun to an otherwise gun-free conflict only to have that gun wrested away and turned on them.

Those explanations, however, will be left to the University of Pennsylvania's Department of Psychology and others to ponder. That institution's biostatisticians and epidemiologists, however, have produced a purely statistical result: if you're packing heat, and someone assaults you with a gun, you're more likely to be shot than if you were unarmed. ®