When it comes to suicide in Wyoming, guns often take the blame as a contributing factor. So does the isolation and flinty independence of rural culture. But a possible cause now being looked at appears to be a more important contributor to self-inflicted deaths: altitude.

Researchers at the University of Utah have found a correlation between how high above sea level people live and per capita suicide rates. Between 1999 and 2007, Wyoming had the fourth-highest rate of suicides per capita in the nation, according to the Centers for Disease Control and Prevention; states in the Mountain West hold nine of the top 10 spots.

The researchers looked at 35 separate factors that could cause suicide. Using suicide data from the CDC and mapping data by the National Aeronautics and Space Administration, they found a distinct correlation between elevation and suicide.

“The Rocky Mountain states just jumped out at you,” said Dr. Perry Renshaw, a professor at the university who took part in the research. “No matter what we did, the altitude kept coming up with a significant factor.”

The study shows that suicides occur between 60 and 70 percent more frequently at high elevations compared to sea level, according to Renshaw.

In fact, altitude surpassed both the isolation of rural culture and the prevalence of gun ownership, both of which come up as assumed causes for the high suicide rate, according to Renshaw. Altitude was the second-highest ranking of 35 variables. The only suicide indicator that ranked higher was being a single mother, he said.

Renshaw, who has spent 15 years studying brain chemistry, said lower oxygen levels in the brain affect people with depression and bipolar disorder.

Both of those disorders involve problems with how the brain uses energy, according to Renshaw. Recent research suggests that the amount of oxygen a person receives affects their mental faculties and performance.

“In depression, what we find is that there are changes in these high-energy compounds in the brain,” Renshaw said.

While oxygen makes up the same percentage of air at sea level as it does at high altitudes, atmospheric pressure — the amount of molecules compressed into one space — decreases with height.

That means people take in fewer oxygen molecules with each breath in a city like Casper, which is a mile above sea level, compared to someone living at sea level.

Comparisons outside the U.S.

To prove the data wasn’t just a fluke, Renshaw and the researchers looked overseas to prove their hypothesis. They did this by analyzing suicide rates in a mountainous country with an elevation that at its highest reaches 6,398 feet: South Korea.

“It was exactly the same result,” Renshaw said, referring to a comparison of suicides in South Korea with the Mountain West. “The higher you went, the higher the result.”

The research also plays into anecdotal stories Renshaw said he has heard about mental illnesses and attitude.

“The other story that I’ve heard a great deal,” Renshaw said, was “moving from sea level to a high-altitude state and becoming depressed for the first time in people’s lives.”

Resistance to findings

The research was initially rejected in the scientific community.

It took some time for the research to be published, as it eventually was in the American Journal of Psychiatry in September 2010. It gained further publicity in the media.

Alan Berman, executive director of the American Association of Suicidology, said multiple factors — those that typically surface in this discussion — contribute to suicide in the Western states.

“Among all the possible explanations, I think it’s probably much further down the list of good explanations,” Berman said.

The rural culture found out West can lead to greater isolation and an unwillingness to ask for help, he said.

“There’s more of a frontier spirit, there’s maybe more of a machismo,” Berman said.

Berman also argued that comparing suicide rates in South Korea to the Western states is not a broad enough foundation to explain a link between suicide and high altitudes.

“If you examine [the link] in other countries, it doesn’t always hold up,” he said.

Berman also said that since Wyoming’s population is predominantly white with some American Indians, suicide may be more demographically prevalent. That is because white and American Indian males often have higher suicide rates, according to Berman.

Renshaw said he was surprised at the resistance to his team’s study.

“It was very difficult to gain acceptance for the research,” he said. “Anytime you have a new idea, it’s going to be looked at more skeptically.”

Possible solution

Researchers now are looking at possible remedies to diminish the altitude-based suicide risks.

Feeding people creatine, an amino acid present in much living tissue that helps supply energy for muscular contraction, seems to help, according to Renshaw.

Of course, finding and targeting those who need the help will be part of the process, since most people don’t have trouble with Wyoming’s high altitude and the mental health issues that are significant contributing factors to suicide.

About five percent of American adults in 2008 were diagnosed with a serious mental illness, according to the National Institute of Mental Health. Not all of those mental illnesses, however, may be affected by altitude.

In short, altitude may not have an adverse affect on the majority of people in Wyoming.

“Most people adjust and are perfectly fine,” Renshaw said. “Most people who live in the Rocky Mountain states are actually very happy.”

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Reach reporter Joe O’Sullivan at 307-266-0639 or joe.osullivan@trib.com. Read his blog at http://trib.com/news/opinion/blogs/osullivan. Follow him on Twitter: @caspercityjoe