"Two recent preliminary studies that found a positive correlation between altitude and suicide relied on the average or highest state altitude, or the elevation of the state capital city, to represent the altitude of the entire state.
However, US states vary greatly in altitude, and this method severely minimizes this variation, Dr. Brenner's team points out. Because counties vary considerably less in altitude than an entire state, they reexamined the altitude-suicide link at a county level.
The investigators included all 2584 US counties in their analysis. They examined county-specific mortality data for 20 years (1979-1998) and determined altitude for each county using the US Geologic Survey.
During the study period, among 42,868,100 total deaths, there were 596,704 suicide deaths (1.4%).
There was a negative correlation between county altitude and all-cause mortality (r = −0.31; P < .001), yet a "strong positive correlation" between county altitude and suicide rate (r = 0.50; P < .001). Positive correlations were seen for both firearm-related suicides (r = 0.40; P < .001) and non–firearm-related suicides (r = 0.31; P < .001).
Prior reports of increased suicide rates in the US mountainous region have fueled speculation that the excess may be due to greater access to firearms, increased isolation, or reduced income. But even after controlling for these variables, the positive correlation between altitude and suicide still exists, they report."