Epidemiol Rev. 2016;38(1):62-9. doi: 10.1093/epirev/mxv011. Epub 2016 Jan 13.
Despite the magnitude and consistency of risk estimates in the peer-reviewed literature linking firearm availability and suicide, inferring causality has been questioned on the theoretical basis that existing studies may have failed to account for the possibility that members of households with firearms differ from members of households without firearms in important ways related to suicide risk. The current bias analysis directly addresses this concern by describing the salient characteristics that such an unmeasured confounder would need to possess in order to yield the associations between firearm availability and suicide observed in the literature when, in fact, the causal effect is null. Four US studies, published between 1992 and 2003, met our eligibility criteria. We find that any such unmeasured 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. No such confounder has been found or even suggested. The current study strongly suggests that unmeasured confounding alone is unlikely to explain the association between firearms and suicide.
尽管同行评议文献中大量且一致的风险评估将枪支的可获得性与自杀联系起来，但基于现有研究可能未能考虑到有枪支的家庭与没有枪支的家庭在与自杀风险相关的重要方面存在差异的理论基础，推断因果关系一直受到质疑。当前的偏差分析通过描述这样一个未被测量的混杂因素需要具备的显著特征来直接解决这一问题，这些特征是为了在实际上因果效应为零的情况下，产生文献中观察到的枪支可获得性与自杀之间的关联。四项在美国发表的研究，发表时间在 1992 年至 2003 年之间，符合我们的入选标准。我们发现，任何这样的未被测量的混杂因素都需要具备难以承受的特征组合，例如不仅是 1）与自杀关系最紧密的精神障碍（例如，重度抑郁和物质使用障碍）一样强有力的自杀风险因素，而且 2）在有枪和没有枪的家庭之间的失衡程度比任何已知的风险因素都要大一个数量级。目前还没有发现或甚至提出这样的混杂因素。本研究强烈表明，未被测量的混杂因素不太可能单独解释枪支与自杀之间的关联。
