Article Summary: Changes in permit-to-purchase laws associated with changes in suicide rates in two U.S. states
Citation: Crifasi, CK, Speed Meyers, J, Vernick, JS & Webster, DW. Effects of changes in permit-to-purchase handgun laws in Connecticut and Missouri on suicide rates. Preventive Medicine 2015;79:43-49
In 2013, more than 40,000 people died by suicide in the U.S. and over half of these deaths involved firearms. Because suicidal thoughts are often transient, means restriction for firearms may be an effective way to prevent suicides. One method of means restriction is implementing permit-to-purchase (PTP) laws that require would-be handgun purchasers to apply for and receive a permit from the state government in order to buy a firearm. Missouri enacted a PTP law in 1921, but repealed it in 2007. Connecticut enacted a PTP law in 1995.
This study used a quasi-experimental design to examine annual state-level suicide rates and counts before and after the Missouri and Connecticut PTP laws changed. The authors compared data from the two intervention states to data from control states whose PTP laws did not change during the study period. Suicide data from 1981-2012 were obtained from the Centers for Disease Control and Prevention's Web-based Injury Statistics Query and Reporting System (WISQARS). Synthetic control methodology was used to estimate the effects of PTP law changes separately in Missouri and Connecticut. Separate analyses were conducted for suicides by firearm and suicides by other methods.
Overall, the two intervention states and their synthetic controls were very similar with respect to baseline suicide rates and predictors. Analyses found the estimated effect of Connecticut's PTP law was a 15.4% decrease in firearm suicide rates during the 10-year period after the law was enacted. There was little estimated effect of the PTP law on non-firearm suicides during the same period. In contrast, the estimated effect of the repeal of Missouri's PTP law was a 16.1% increase in firearm suicide rates and a 15.0% increase in non-firearm suicides during the 5-year period after the repeal.
A major limitation of this study is the possibility that associations between suicide rates and changes in PTP laws were confounded by some other factor(s). This is a common problem in evaluations of public policy. A second limitation is synthetic control methodology does not provide a p-value or confidence interval for the estimates; however, the authors argued this method enabled them to most accurately select comparison states. Using synthetic controls also allowed for controlling state demographic characteristics that could be associated with risk of suicide (e.g., proportion of veterans). The authors argued the strengths of this study outweigh its limitations.
In the decade following the implementation of a permit-to-purchase (PTP) law in Connecticut, firearm suicide rates declined by an estimated 15.4%. In Missouri, the repeal of a PTP law was associated with an estimated 16.1% increase in firearm suicide rates and an estimated 15.0% increase in non-firearm suicide rates over five years.