Table 2.

Regression discontinuity analysis estimates for limiting handgun sales to purchasers age 18, relative to age 21 or older and suicides

Variables	Incident rate ratio (95% CI)
Treated (age 18-20 in states with age 18 limit on handgun sales, binary)	1.26 (1.10 to 1.45)
Treated×continuous age	1.09 (1.03 to 1.16)
Age (continuous)	1.09 (1.04 to 1.14)
Age2 (continuous)	0.96 (0.95 to 0.97)

Estimates are based on negative binomial regression analyses with log population as an offset. Data are from all states from 1999 to 2017 and are weighted based on state population size. Based on predicted probabilities, an average of 344 suicides would have been averted in each state between 2001 and 2017 among adolescents aged 18 to 20 years with policies restricting the minimum age of handgun sales to age 21 years relative to age 18 years.