Sept. 22, 2010  -- Is it possible that living in the mountains can make it more likely that someone will commit suicide? Maybe, according to startling new research suggesting that for someone who already has mental health problems, thinner air may be one factor leading to self destruction.

That finding may seem a bit baffling at first blush, but psychiatrist Perry F. Renshaw of the University of Utah said his team of researchers have found an "astonishingly strong" correlation between living at higher altitudes and the suicide rates across the country. The data had been collected by various agencies between 1979 and 1998.

"We mapped the altitude of all of the counties in the United States and looked at suicide rates over that 20-year period and the association was extraordinarily strong statistically," Renshaw said in a telephone interview.

The data may help explain why the Rocky Mountain states and others with high elevations in the western part of the country consistently report the highest rates of suicide per 100,000 persons. Alaska, Montana, New Mexico, Colorado, Utah and Nevada rank in the top 10 suicide states year after year after year.

Why Might Thin Air Contribute to Higher Suicide Rates?

Renshaw, senior author of a study just published in the American Journal of Psychiatry and a specialist in brain imaging, offered one possible explanation for why thin air may contribute to higher suicide rates.

"I worked on the east coast for many years, studying brain chemical changes associated with depression," he said.

Depression has been linked to suicide in at least 60 percent of the cases, he added, so he was intrigued when he detected chemical changes in the brains of depressed people that had an effect on metabolism, the sum of the physiological processes that make it possible for an organism to grow new cells and tissues, and generate the energy necessary to maintain life.

Renshaw's working hypothesis is that thin air contributes to mild hypoxia, metabolic stress caused by inadequate levels of oxygen, which may in turn aggravate existing mental health problems. So there's no suggestion here that moving to the mountains may cause a mentally healthy person to commit suicide, but he believes that in some cases it may be a significant risk factor.

Suicide Is Complex, Experts Say

Suicide is an extremely complex phenomenon, he noted, and there are many other factors. Availability of firearms, which are used in most suicides, and drug and alcohol abuse, as well as overall mental health, are certainly leading causes. But he thinks his team has found a new contributor.

Only one other team, at Case Western Reserve University, has found a link between elevation and suicide, but their complete work has not yet been published. So this is "uncharted territory," as Renshaw put it.

Renshaw's team has repeated its findings in two other mountainous countries, Italy and South Korea. The lead author of the study, Namkug Kim, is from South Korea and had access to data banks there.

"South Korea has a very high suicide rate, first or second highest in the world, and South Korea has a tremendous range in altitude from sea level up to several thousand meters," Renshaw said. "We found the same thing there. The higher the altitude, the higher the suicide rate."

The Utah study began a couple of years ago when Renshaw heard a talk by a suicide specialist who presented maps of suicide rates in the United States.

Scientist: Suicide Rates in Some Mountainous States 'Popped'

"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.

Leading Causes of Suicide in Mountainous States May Vary

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.

Rural Communities Vulnerable to Suicide

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.