State handgun purchase age minimums in the US and adolescent suicide rates: regression discontinuity and difference-in-differences analyses.

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.