• Empirical study of firearm possession and suicides at the state-level over 2000–2009.
• Firearms are found to be very strongly related to firearm suicides, as expected.
• Firearms are also found to be strongly related to overall suicides, despite evidence for substantial substitution in method of suicide.
• There is evidence for a diminishing effect of guns on suicides as ownership levels increase.
• The results hold using instrumental variables estimation, a variety of measures of gun ownership, and across a variety of sets of controls.

“Firearms play a unique role in public discourse. The US Constitution protects the right to bear arms. For some, this right represents an important safeguard against tyranny. For hunters and sportsmen, firearms enable a vibrant recreation. Firearms also play an important but largely unknown role in self-defence. Yet in 2010, the latest year for which there are complete figures, there were 19,392 suicides, 11,078 homicides, and 606 accidental deaths by firearm, in addition to 73,505 non-fatal injuries by firearms (Centers for Disease Control and Prevention, 2012). Unfortunately, even basic information such as how many households own firearms is irregular and partly as a result there is little scientific consensus on how firearms influence violent injuries. Although the effect of firearms on homicides has been a topic of recurring debate, less attention is often given to suicide, despite there being more deaths attributable to suicide than to homicide. This may be in part because people view suicide as a private decision only affecting friends and family of the deceased, although this impact should not be minimized. But many psychological studies find that suicides are frequently impulsive decisions (e.g. Simon et al., 2002), and that less than 10% of suicide survivors go on to successfully re-attempt suicide over the long term (Owens et al., 2002). Few suicides appear to be considered choices.  In this study we specifically explore the relationship between firearm ownership rates and rates of suicide, using a newly constructed dataset covering US states from 2000 to 2009. We utilize all data from the first state-level representative survey of gun ownership, as well as four other proxies thereof, including one new to the literature. In addition, we will develop instruments for firearm ownership rates.”