Here is an abstract from a scientific publication, Rebekah S Huber et al. (including Perry Renshaw, mentioned below), "Altitude is a Risk Factor for Completed Suicide in Bipolar Disorder," Medical Hypotheses, 82/3 (March 2014): 377–381:
Bipolar disorder (BD) is a severe brain disease that is associated with a significant risk for suicide. Recent studies indicate that altitude of residence significantly affects overall rate of completed suicide, and is associated with a higher incidence of depressive symptoms. Bipolar disorder has shown to be linked to mitochondrial dysfunction that may increase the severity of episodes. The present study used existing data sets to explore the hypothesis that altitude has a greater effect of suicide in BD, compared with other mental illnesses. The study utilized data extracted from the National Violent Death Reporting System (NVDRS), a surveillance system designed by the Centers for Disease Control and Prevention (CDC) National Center for Injury Prevention and Control (NCIPC). Data were available for 16 states for the years 2005–2008, representing a total of 35,725 completed suicides in 922 U.S. counties. Random coefficient and logistic regression models in the SAS PROC MIXED procedure were used to estimate the effect of altitude on decedent’s mental health diagnosis. Altitude was a significant, independent predictor of the altitude at which suicides occurred (F = 8.28, p=0.004 and Wald chi-square=21.67, p < 0.0001). Least squares means of altitude, independent of other variables, indicated that individuals with BD committed suicide at the greatest mean altitude. Moreover, the mean altitude at which suicides occurred in BD was significantly higher than in decedents whose mental health diagnosis was major depressive disorder (MDD), schizophrenia, or anxiety disorder. Identifying diagnosis-specific risk factors such as altitude may aid suicide prevention efforts, and provide important information for improving the clinical management of BD.The first such study I am aware of is C.A. Haws et al. (including Perry Renshaw), "The possible effect of altitude on regional variation in suicide rates," Medical Hypotheses, 73/4 (Oct. 2009): 587-90, with this abstract:
In the United States, suicide rates consistently vary among geographic regions; the western states have significantly higher suicide rates than the eastern states. The reason for this variation is unknown but may be due to regional elevation differences. States' suicide rates (1990-1994), when adjusted for potentially confounding demographic variables, are positively correlated with their peak and capital elevations. These findings indicate that decreased oxygen saturation at high altitude may exacerbate the bioenergetic dysfunction associated with affective illnesses. Should such a link exist, therapies traditionally used to treat the metabolic disturbances associated with altitude sickness may have a role in treating those at risk for suicide.Now a variety of additional studies have been published, with several cited in the Huber et al. article above. The lower concentration of oxygen at high altitudes can have an effect on serotonin and while that can be positive for many people, it can exacerbate or contribute to depression for others. Multiple studies now point to altitude as having a significant effect on suicide. There is still more to understand and debate, but this is a noteworthy development.
Such findings are gradually making it into popular media, though I suspect that many of us haven't heard much about this yet. One very readable and interesting report is Theresa Fisher, "There's a Suicide Epidemic in Utah — And One Neuroscientist Thinks He Knows Why," Mic.com, Nov. 18, 2014 (a hat tip to Russell Osmond for this article and motivation for my post). For a Wyoming perspective, see Joe O'Sullivan, "Altitude may be major factor in suicide," Casper Star-Tribune, Sept. 18, 2011. An excerpt follows:
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.O ye mountains high, indeed!
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.”
Understanding the impact of altitude for those facing depression or other mental health challenges may now help guide medical professionals in better assisting patients, including single mothers (being a single mother turned up in one study as just about the only risk factor more significant than altitude). If nothing else, getting away to a lower altitude area for a while might be a big help. We'd love to see you here in Shanghai, a place where you may find it's a good thing to have friends in low places.
Update, June 3, 2018: Some readers questioned why Colorado or the Andes weren't considered. Renshaw's work has considered the entire Mountain West and also many nations, and has seen the altitude effect repeatedly.
A very recent publication involving the Andes, not done by Renshaw, also points to a possible altitude effect, though the authors don't seem familiar enough with Renshaw's work to explain why an altitude effect might exist. See Esteban Ortiz-Prado, "The disease burden of suicide in Ecuador, a 15 years’ geodemographic cross-sectional study (2001–2015)," BMC Psychiatry, 17(2017): 342; doi: 10.1186/s12888-017-1502-0. They found that "Provinces located at higher altitude reported higher rates than those located at sea level (9 per 100,000 vs 4.5 per 100.000)." A much higher suicide rate for the high-altitude provinces.
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