Could there be a correlation between high altitudes and mental health problems?

A new review of research, titled "Living High and Feeling Low: Altitude, Suicide, and Depression," was published in the journal Harvard Review of Psychiatry. The findings suggested when a person's residence is located in high-altitude areas, they may face an increased risk of suicide and major depressive disorder.

Brent Michael Kious from the University of Utah, along with his colleagues, analyzed 12 studies as a part of the review.

A majority of the studies, including population-based data on the relationship of altitude with suicide or depression, were conducted in the United States. It was observed the states which had the highest suicide rates were clustered in the intermountain areas of Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming. High suicide rates were also seen in Alaska and West Virginia. In general, the correlation was stronger for suicide than for depression.

While 80 percent of suicides in the U.S. occurred in low altitude areas, the figure can be misleading as majority of the population settled down near sea level. When looking at suicide rates per 100,000 population, figures indicate 17.7 at high altitude, 11.9 at middle altitude, and 4.8 at low altitude. A study from 2014 also showed the percentage of adults with "serious thoughts of suicide" ranged from 3.3 percent in Connecticut (average altitude 490 feet) to 4.9 percent in Utah (average altitude 6,100 feet).

Suicide rates increased dramatically at altitudes between 2,000 and 3,000 feet, which the study referred to as a threshold effect. Populations living in these higher altitudes saw increased suicide rates despite having decreased rates of death from all causes. The study claims altitude may also affect other psychiatric conditions such as attention-deficit/hyperactivity disorder (ADHD) as the prevalence of ADHD was shown to decrease with altitude

"There are significant regional variations in the rates of major depressive disorder and suicide in the United States, suggesting that sociodemographic and environmental conditions contribute," Kious and co-authors stated in the review. The researchers also suggested lower blood oxygen levels (due to the low atmospheric pressure) might explain the increased suicide rates.

Relative hypobaric hypoxia, which refers to lower blood oxygen concentration due to lower inhaled oxygen, is a speculated link between altitude, suicide, and depression. The study highlighted how hypoxia affects "both serotonin metabolism and the efficiency of brain bioenergetics, each of which may contribute to depression."

The researchers have expressed the potential for future research to solidify strategies to address hypoxia-related depression and suicidal ideation. Possible treatments may include supplemental 5-hydroxytryptophan to increase serotonin levels, as well as creatinine to influence brain bioenergetics.

Clinical trials were also encouraged where neuroimaging techniques could incorporate genetic markers, and be used to assess brain connectivity and metabolism. This could help determine whether genetic differences also contributed to altitude-related depression.