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Utah researchers say common antidepressants don't work as well at high altitudes

SALT LAKE CITY — It has widely been shown that altitude might have something to do with Utah's high rates of suicide and depression.

Now, researchers at the University of Utah are finding that being a few thousand feet above sea level could also be affecting the medications doctors are using to treat depression and anxiety disorders.

"We may need to be more careful about which antidepressants are prescribed to people living at altitude," said Shami Kanekar, a research assistant professor of psychiatry and a lead author of a study published this month in Pharmacology Biochemistry and Behavior.

Reduced oxygen levels experienced at high elevations, Kanekar said, can worsen levels of depression and lower a person's response to selective serotonin reuptake-inhibitors, called SSRIs, which are the most commonly prescribed antidepressants in the United States.

The high altitude can also make depression worse in some people taking certain SSRIs, Kanekar said.

"The brain's ability to make serotonin is entirely dependent on having enough oxygen to do so," said Dr. Perry Renshaw, professor of psychiatry at the U. and senior author of the study.

He said Utah's atmosphere has around 17 percent less oxygen than at sea level.

"Being at altitudes of 4,000 to 5,000 feet really does reduce brain serotonin levels," Renshaw said, adding that the effects — shortness of breath, headache and rapid heartbeat, among others — can be felt within a couple of hours at altitude.

"It's a lot," he said. "Your body knows it. It starts responding right away. And, if you have a mood or anxiety disorder or there's something in your history with regard to serotonin, this could make a big difference."

Kanekar's animal experiments, involving rats housed at various barometric pressures to mimic different altitudes, show that three very common antidepressants — Paxil (paroxetine), Lexapro (escitalopram) and Prozac (fluoxetine) — could be less effective at high elevations.

The impacts are felt more prominently by women, Renshaw said, as women have half as much serotonin in their brains as do men to begin with. Women also experience more anxiety symptoms than symptoms of depression at high altitudes.

"We find that females in our model are much more sensitive to being housed at altitude than males," Kanekar said.

And it makes sense, as at least 25 percent of all adult women in Utah are prescribed the antidepressants — "hugely above the national average," Renshaw said.

The researchers hope their theory and experimental findings will result in clinical reality, helping people to feel better and experience more relief, as well as avoid suicide.

"We can do a whole lot better recognizing that there are a family of hypoxic illnesses that we're not treating very well," Renshaw said, adding that hypoxia, or not getting enough oxygen, isn't the only thing causing suicide.

Additional factors include health care availability and cost of care, but, he said, "No matter what we throw into the model, altitude comes out as one of the strongest predictors."

Research like the U.'s altitude studies have had trouble gaining traction outside of geographical areas in which the theorized phenomenon occurs, but Renshaw said the same findings have been observed "across the globe and on every continent and among different cultures of people," which may result in more acceptance and therefore, funding.

The U. study is supported by the Utah Science, Technology and Research Initiative and the U.S. Department of Veterans Affairs' Mental Illness Research Education and Clinical Center, which provides resources to veterans, a population believed to experience a high rate of mental illness and suicidality.

Kanekar hopes the results of their ongoing research could help with other hypoxic disorders or diseases that also correlate with high rates of depression and suicide — including asthma, sleep apnea and chronic obstructive pulmonary disease, among others. It might be, she said, that modified or new treatments could improve things.

"We are at this exciting stage where the findings may well inform people to have better lives," Renshaw said.