Department of Health Law, Policy, and Management, Boston University School of Public Health, Boston, MA 02118, USA
Harvard TH Chan School of Public Health, Boston, MA, USA.
BMJ. 2020 Jul 22;370:m2436. doi: 10.1136/bmj.m2436.
To evaluate the association between US state policies that establish age 18 or 21 years as the minimum purchaser age for the sale of handguns and adolescent suicide rate.
Regression discontinuity and difference-in-differences analyses.
46 US states without policy changes between 2001 and 2017; Missouri and South Carolina, which lowered the age for handgun sales in 2007 and 2008, respectively; and West Virginia and Wyoming, which increased the age for handgun sales in 2010.
Adolescents aged 13 to 20 years(554 461 961 from 2001 to 2017) in the regression discontinuity analysis, and adolescents aged 18 to 20 years (168 934 041 from 2002 to 2014) in the main difference-in-differences analysis.
Suicide rate per 100 000 adolescents.
In the regression discontinuity analysis, state policies that limited the sale of handguns to those aged 18 or older (relative to 21 or older) were associated with an increase in suicide rate among adolescents aged 18 to 20 years equivalent to 344 additional suicides in each state where they were in place between 2001 and 2017. In the difference-in-differences analysis, state policies that limited the sale of handguns to those aged 21 or older were associated with 1.91 fewer suicides per 100 000 adolescents aged 18 to 20 years (95% confidence interval -3.13 to -0.70, permutation adjusted P=0.025). In the difference-in-differences analysis, there were 1.83 fewer firearm related suicides per 100 000 adolescents (-2.66 to -1.00, permutation adjusted P=0.002), with no association between age 21 handgun sales policies and non-firearm related suicides. Separate event study estimates indicated increases in suicide rates in states that lowered the age of handgun sales, with no association in states that increased the age of handgun sales.
A clear discontinuity was shown in the suicide rate by age at age 18 in states that limited the sale of handguns to individuals aged 18 or older. State policies to limit the sale of handguns to individuals aged 21 or older were associated with a reduction in suicide rates among adolescents. Increases in suicide rates were observed after states lowered the age of handgun sales, but no effect was found in states that increased the age of handgun sales.
评估美国各州将出售手枪的最低购买年龄设定为 18 岁或 21 岁的政策与青少年自杀率之间的关联。
回归不连续性和差异中的差异分析。
2001 年至 2017 年期间没有政策变化的 46 个美国州；密苏里州和南卡罗来纳州分别于 2007 年和 2008 年降低了手枪销售年龄；西弗吉尼亚州和怀俄明州分别于 2010 年提高了手枪销售年龄。
2001 年至 2017 年期间，年龄在 13 至 20 岁的青少年（554 461 961 人）；2002 年至 2014 年期间，年龄在 18 至 20 岁的青少年（168 934 041 人）。
每 10 万名青少年的自杀率。
在回归不连续性分析中，将手枪销售限制在 18 岁或以上（相对于 21 岁或以上）的州政策与 18 至 20 岁青少年自杀率的增加有关，相当于在 2001 年至 2017 年期间实施这些政策的每个州，自杀人数增加了 344 人。在差异中的差异分析中，将手枪销售限制在 21 岁或以上的州政策与每 10 万名 18 至 20 岁青少年减少 1.91 例自杀有关（95%置信区间-3.13 至-0.70，置换调整 P=0.025）。在差异中的差异分析中，每 10 万名青少年的枪支相关自杀人数减少了 1.83 人（-2.66 至-1.00，置换调整 P=0.002），而 21 岁手枪销售政策与非枪支相关自杀之间没有关联。单独的事件研究估计表明，降低手枪销售年龄的州自杀率有所增加，而提高手枪销售年龄的州则没有关联。
在将手枪销售限制在 18 岁或以上的州，按年龄划分的自杀率显示出明显的不连续性。将手枪销售限制在 21 岁或以上的州政策与青少年自杀率的降低有关。在各州降低手枪销售年龄后，观察到自杀率上升，但在提高手枪销售年龄的州没有发现这种影响。
