"It was quite astonishing in that the rates in the mountainous states along the Rockies just popped," he said. So he and his team began collecting data on suicide rates and elevation across the country. They ended up with information from 3,108 counties, furnished by various agencies, including NASA and the Centers for Disease Control.
The data covers all 48 contiguous states, plus the District of Columbia, but Alaska and Hawaii were not included because of insufficient data.
The findings are general, painting a portrait of the nation as a whole, and it is a little difficult to match individual states with the final results because some conditions vary so much from state to state.
In the case of Utah, where the researchers are based, the "geographic altitude is about 6,000 feet, and the rate of suicide is 70 percent higher [than average,] so it's an astonishing increase in what is a relatively uncommon event, suicide," Renshaw said. So that case is pretty clear.
But in Alaska (this columnist's home state), for example, it is less clear. Alaska led the nation in 2007, the most recent year for which statistics that are available, with 149 suicides out of a population of 681,111. That's a rate of 21.8 suicides per 100,000 population.
Alaska, of course, has many high mountains, but very few residents live above 2,000 feet. By far the majority live at sea level, so thin air is probably not the problem. But much of the state has long winter nights, known to contribute to depression, and alcohol abuse is rampant, especially in the tiny villages of the far north.
And just about everybody has at least one gun. So the causes of suicide are indeed complex, and leading causes in Alaska, and Utah, may be quite different than in Nevada, which led the list in 2006.
A study led by Temple University sociologist Matt Wray in 2008 found that people who live in Las Vegas face a much greater suicide risk than the national average. But Vegas is only 2,000 feet above sea level, so the air there is not thin. But it is Vegas, after all, where dreams can die with the roll of the dice.
Vegas is also a place where it's pretty easy to get a drink, at least of alcohol. Another study last year revealed that people with alcohol dependence accounted for 20 percent of suicides in the general population, and that research linked the high rate of suicides to the number of bars.
That study found the highest suicide rates occurred in rural communities with lots of bars.
Thus there's more at work than just a Rocky Mountain high, as alluded to by the late John Denver. Rural communities are particularly vulnerable to suicide, according to several studies, possibly due to isolation.
Renshaw's team concludes its study with this warning:
"Despite the very strong associations between suicide and altitude of residence, the data we present here should be interpreted cautiously." Correlation is not necessarily causation, and they note that the causes of suicide "vary with age, sex, ethnicity, socioeconomic factors, psychiatric illness, family history" and on and on.
But if this research can be confirmed by others, there's a new player in this tragic theater.