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Epidemiologic Reviews
Focuses On The Science Related To Guns

We Have Learned Useful But Still Only Limited Information Because Of Congressional Threats

A striking conclusion from a special issue of Epidemiologic Reviews devoted to examining the science on gun violence is that there is too little science to begin with. So says Michel Ibrahim, Johns Hopkins epidemiologist and co-editor of the violence issue.   According to Ibrahim, “epidemiologic research on gun violence is scarce, especially research with powerful study designs such as prospective cohort studies. Several papers in the issue [of Epidemiologic Reviews] addressed violence generally and attempted to extrapolate to gun violence. “

Evidence Shortfall

A frequently cited reason for the shortage is the belief that Congress has mandated against it. But according to Daniel Webster, a second co-editor of the special issue and Director of the Hopkins Center for Gun Policy and Research, “ … it is not accurate to say that there has been a ban on federally funded research on gun violence.  There is no piece of legislation that says that these agencies can’t use their funds designated for broad categories (e.g., youth violence, domestic violence, gang violence, substance abuse and violence) to support research that examines guns and gun violence.  The National Institute of Justice and to a much lesser degree the CDC and NIH have funded research studies on gun violence during the past 20 years. But these agencies have, for the most part, decided to avoid

 funding any study that has the potential to offend the gun lobby in order to avoid budget cuts that members of Congress threaten if they don’t like the research or the findings.  It was the efforts to cut the budget of the CDC and, initially, to completely eliminate its Center for Injury Prevention and Control, that has led to restricted (both in $ and research question) funding.”

Staggering Toll

"There is widespread concern about the staggering toll of gun violence in the U.S., according to Ibrahim.

In the year 2013 alone, firearms were responsible for 11,208 deaths by homicide (3.5 per 100,000 citizens). While homicides by firearm occur less frequently in the US than, for example, in Columbia (38.1 per 100,000 citizens), many are surprised to find that they are on par with countries such as Nicaragua (34.86 per 100,000 citizens), Palestine (3.09 per 100,000 citizens) and Uganda (3.71 per 100,000 citizens). These numbers also don’t account for non-lethal firearm induced trauma, both mental and physical, and the 21,175 suicide deaths by firearm (6.7 per 100,000 citizens).

Gun Access & Suicide

An important topic addressed in one of the articles is the relationship between firearm access and suicide rates. Is this relationship causal or the result of a confounder? Using a bias analysis, the authors of the article determine that a “confounder would need to possess an untenable combination of characteristics, such as being not only 1) as potent a suicide risk factor as the psychiatric disorders most tightly linked to suicide (e.g., major depressive and substance use disorders) but also 2) an order of magnitude more imbalanced across households with versus without firearms than is any known risk factor.” As such, they believe it is highly unlikely that such a confounder exists and has gone undetected to date. Thus firearm accessibility alone is likely the cause of increased suicide rates in homes where firearms are kept.

Substance Abuse

Three of the articles examine the relationship between substance use and gun-related behaviors. A causal relationship between substance abuse and gun violence has long been assumed and a federal law prohibits the purchase of firearms by those that unlawfully use or are addicted to illegal substances. However, defining individuals to exempt from gun purchasing under this definition is still a gray area due to the presence of confounders. For example, positive associations between substance use and gun violence disappear or decrease when data is adjusted for psychiatric disorders. That said, interventions can be effective even without complete understanding of the causal relationship. It remains that drug selling and firearm usage are positively correlated, so limiting firearm access for drug sellers may have positive outcomes even if the underlying cause is rooted in psychiatric disorders which, consequently, are much more difficult to identify.

Social Networks

Another interesting review showed that the likelihood of gun victimization or perpetration is predicted by social network distance from individuals who use guns. The review demonstrated the potential of social network analysis to predict gun violence and guide prevention efforts.

Impact of Interventions

Studies reviewed in the issue show that the effectiveness of firearm safety screening and counseling can be achieved through clinician training and that patients and families are accepting of such counseling, however the authors reviewing the material believe that higher quality studies are needed. Additionally, another article demonstrates that counseling and device provision successfully encourage the safe storage of firearms. Lastly, the final article in the issue tackles a characterization of the global effects of gun laws in a review of 130 studies carried out in 10 different countries between 1950 and 2014. The authors believe that, “high quality research on the association between the implementation or repeal of firearm legislation (rather than the evaluation of existing laws) and firearm injuries would lead to a better understanding of what interventions are likely to work given local contexts.”

Editor’s Overall Take

According to Ibrahim, “several of the studies reviewed used ecological, cross-sectional, and before-after designs, which, because of the inherent confounding factors, limited the degree of certainty and generalizability of the results. In spite of these limitations, the weight of the evidence points to plausible relationships between guns access and suicide, between deviant social networks and gun violence, and between restrictive gun legislation and reduced deaths. Better designed epidemiologic studies would provide more firm conclusions.” He added “the strongest evidence of benefit comes from reviews (some used randomized trials) about clinicians’ practices that encourage safe gun behaviors that were shown to be effective strategies.”


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