OBJECTIVE In this study, we analyzed the relationship between state firearm laws and the incidence and severity (i.e., number of victims) of mass public shootings in the United States during the period 1976-2018. HYPOTHESES We hypothesized that states requiring permits to purchase firearms would have a lower incidence of mass public shootings than states not requiring permits. We also hypothesized that states banning large-capacity ammunition magazines would experience a lower number of victims in mass public shootings that did occur than states without bans. METHOD We developed a panel of annual, state-specific data on firearm laws and mass public shooting events and victim counts. We used a generalized estimating equations logistic regression to examine the relationship between eight state firearm laws and the likelihood of a mass public shooting. We then used a zero-inflated negative binomial model to assess the relationship between these laws and the number of fatalities and nonfatal injuries in these incidents. RESULTS State laws requiring a permit to purchase a firearm were associated with 60% lower odds of a mass public shooting occurring (95% confidence interval [CI: -32%, -76%]). Large-capacity magazine bans were associated with 38% fewer fatalities (95% CI [-12%, -57%]) and 77% fewer nonfatal injuries (95% CI [-43%, -91%]) when a mass shooting occurred. CONCLUSION Laws requiring permits to purchase a gun are associated with a lower incidence of mass public shootings, and bans on large capacity magazines are associated with fewer fatalities and nonfatal injuries when such events do occur. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

中文翻译：

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1976-2018 年美国各州枪支法与大规模公共枪击事件的发生率和严重程度之间的关系。

目的 在本研究中，我们分析了 1976 年至 2018 年期间美国各州枪支法与大规模公共枪击事件的发生率和严重程度（即受害者人数）之间的关系。假设 我们假设需要购买枪支许可证的州比不需要许可证的州发生大规模公共枪击事件的发生率要低。我们还假设，禁止大容量弹匣的州在大规模公共枪击事件中的受害者人数会比没有禁令的州少。方法 我们开发了一组关于枪支法、大规模公共枪击事件和受害者人数的州特定年度数据。我们使用广义估计方程逻辑回归来研究八个州枪支法与大规模公共枪击事件的可能性之间的关系。然后，我们使用零膨胀负二项式模型来评估这些法律与这些事件中的死亡和非致命伤害人数之间的关系。结果 要求购买枪支需要许可证的州法律与大规模公共枪击事件发生的几率降低 60% 相关（95% 置信区间 [CI: -32%, -76%]）。大规模枪击事件时，大容量弹匣禁令可减少 38% 的死亡人数（95% CI [-12%, -57%]）和 77% 的非致命伤害（95% CI [-43%, -91%]）发生。结论 要求购买枪支获得许可的法律与大规模公共枪击事件的发生率较低有关，而禁止使用大容量弹匣则与此类事件发生时死亡和非致命伤害的减少有关。（PsycInfo 数据库记录 (c) 2020 APA，保留所有权利）。