In 2004, the U.S. National Academy of Sciences released its evaluation from a review of 253 journal articles, 99 books, 43 government publications, and some original empirical research. It failed to identify any gun control that had reduced violent crime, suicide, or gun accidents...

Thus both sides of the gun prohibition debate are likely wrong in viewing the availability of guns as a major factor in the incidence of murder in any particular society. Though many people may still cling to that belief, the historical, geographic, and demographic evidence explored in this Article provides a clear admonishment. Whether gun availability is viewed as a cause or as a mere coincidence, the long term macrocosmic evidence is that gun ownership spread widely throughout societies consistently correlates with stable or declining murder rates. Whether causative or not, the consistent international pattern is that more guns equal less murder and other violent crime. Even if one is inclined to think that gun availability is an important factor, the available international data cannot be squared with the mantra that more guns equal more death and fewer guns equal less death. Rather, if firearms availability does matter, the data consistently show that the way it matters is that more guns equal less violent crime. (emphasis in original).

Kates and Mauser, 2006. The authors have similar findings for the relationship between suicide and firearms ownership:

The mantra more guns equal more death and fewer guns equal less death is also used to argue that "limiting access to firearms could prevent many suicides." Once again, this assertion is directly contradicted by the studies of 36 and 21 nations (respectively) which find no statistical relationship. Overall suicide rates were no worse in nations with many firearms than in those where firearms were far less widespread.