Augustine J. Kposowa of the University of California, Riverside, and colleagues analyzed mortality data from the U.S. Multiple Cause of Death Files for 2000-04 and combined individual-level data with state-level information.
Firearm ownership, conservatism -- measured by percentage voting for former President George W. Bush in the 2000 election, suicide rate, church adherence and immigration rate were measured at the state level.
Kposowa and colleagues analyzed data relating to 131,636 individual suicides, which were then compared to deaths from natural causes -- excluding homicides and accidents.
"Many studies show that of all suicide methods, firearms have the highest case fatality, implying that an individual who selects this technique has a very low chance of survival," Kposowa said. "Guns are simply the most efficient method of suicide."
The study, published in the journal Social Psychiatry & Psychiatric Epidemiology, found with few exceptions, states with the highest rates of gun ownership -- Alaska, Montana, Wyoming, Idaho, Alabama and West Virginia -- also tended to have the highest suicide rates. These states were also carried overwhelmingly by George Bush in the 2000 presidential election, the study said.
The study also found the odds of committing suicide were almost three times higher among men than women, non-Hispanic whites were nearly four times as likely to kill themselves as non-Hispanic African-Americans and the odds of suicide among Hispanics were 2.3 times higher than the odds among non-Hispanic African-Americans.
Divorced and separated individuals were 38 percent more likely to kill themselves than those who were married, while a higher percentage of church-goers at the state level reduced individual suicide risk, the study said.
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