Effects of Altitude on Anxiety

Over the years, there have been extensive amounts of research done surrounding the impact of altitude on humans in a relatively short-term context, particularly as it related to athletic training at higher altitudes. While the symptoms of "altitude sickness" might be familiar, including nausea, lightheadedness, dizziness, headache, and fatigue, it is not as well known that increased anxiety can also occur. While a number of investigations of the effects of altitude on anxiety have been conducted in humans (Gertsch et al. 2011; Fagenholz et al. 2007), fewer have been conducted using animal models.

         During undergrad, I was fortunate enough to be brought on board to help with a study attempting to fill these gaps in research by looking at the effects of different altitude acclimation periods on anxiety in rats. In what my PI liked to refer to as the "mother of all studies", we looked at 320 rats, which included both male and female animals, as well as two different animal strains, and five different weeks of acclimation. These rats participated in three different behavioral tests, two of which looked at indications of depression and one that focused on indicators of anxiety; my role in the study focused more on the anxiety aspect. For our control, half of these animals underwent behavioral testing at sea level in La Jolla, CA. The other half of the animals were tested at altitude in Boulder, CO.

         While the design of this study is complicated to explain in a short amount of text with so many moving parts, the potential implication and importance of this project aren’t as difficult. First, there is little research on the physiological and behavioral effects of changes in altitude on rats, which is surprising considering that most laboratory rat vendors are located near sea level. Understanding the effects of these changes should be of particular interest to minimize confounding variables and maximize reproducibility in studies. Research has been done on a short-term scale to set controls for shipping-induced stress of laboratory animals, indicating a minimum 48-hour stabilization period upon arrival (Landi et al. 1982), but altitude has not been considered a factor when considering this stabilization period thus far. Second, female rats were chosen to be included in this study since they are often underrepresented in research; many researchers opt to use male animals only to rule out the potential hormonal effects that can be a confounding factor in behavioral studies. Two of the most commonly used rat strains were also included to observe any differences.

         In this study, we hypothesized that higher altitude would increase the levels of anxiety and depression. With the extremely large set of data that we collected, analysis has proven to be an incredibly long process, so we are still awaiting clear-cut results.

Gertsch J, Virre E, Sracic M, Pate A, Thomas D (2011) Acute Anxiety Among Marines

After Recent Arrival at High Altitude: High Altitude Anxiety as a Distinct Diagnostic

Entity. Wilderness & Environmental Medicine, 22(4): 356-357.

Fagenholz P, Murray A, Gutman J, Findley J,  Harris N (2007) New-Onset Anxiety Disorders at High Altitude. Wilderness & Environmental Medicine, 18(4): 312-316.

Landi MS, Kreider JW, Lang CM, Bullock LP (1982) Effects of shipping on the immune

function in mice. Amer. J Vet Res, 43(9):1654-1657.