Every night, Audrey Hart breathes in a flow of 50 percent oxygen at two liters a minute from a tube connected to a white machine the size of a toaster oven. She keeps it in her bedroom to use while she falls asleep. She bought the machine on Amazon for around $500 in August of 2017, a month after she came the closest she ever had to killing herself. “You get to that low where it's just so consuming that you honestly feel like the world is better off without you,” the 36-year-old said. “Life is not worth living because no one wants you here.”

But critics of the theory say that suicide from low oxygen is too simple of an explanation, and ignores the overwhelming sociocultural attributes of these areas—access to guns, poverty, social isolation, a dearth of mental health services. In Utah, the Mormon Church can also be a suffocating presence that has a heavy impact on LGBTQ youth. The skeptics worry that an over-focus on the fringe physiological influence of altitude could distract from getting people the help they need, and put the focus instead on oxygen machines and supplements.

One thing that these states have in common is high elevations. In 2011, a handful of scientists from Utah put forth a provocative theory: that the high altitudes are contributing to the high suicide rates. They said that a lack of oxygen can lead to hypoxia, or oxygen deprivation, and affect fundamental processes of the brain, like the production of the neurotransmitter serotonin, which is thought to play a key role in mood. They think it could also potentially affect the functioning of depression medications like SSRIs.

In addition to now taking medication for depression, Hart supplements with oxygen—an idea that came from published studies out of the University of Utah, close to her home near Salt Lake City. Researchers there are trying to explain a long-observed phenomenon: that suicide rates are much higher in certain parts of the western United States. Of the 10 states with the highest suicide rates, eight are in a region darkly deemed “the suicide belt.” In the heat map of suicide deaths from the CDC, the suicide belt cuts across the country in dark red—including Colorado, Montana, Utah, Idaho, and Wyoming.

One night in July of 2017, when she was ready to end her life, Hart's two daughters, 7 and 8, ran up and hugged her. She said their embrace is what saved her. Shortly after, her husband Ryan read one of the studies coming out of the university, and pushed for her to start getting more oxygen. He said to her: “I think there's a serious correlation here. I think it's worth buying an oxygen machine for you."

In 2017, suicide was the leading cause of death for people in Utah ages 10 to 24, and it was the second leading cause of death for people 25 to 44. The rate of teen suicide in Utah is more than double the national rate, and its youth suicide rate has tripled over the past 10 years. More young people die of suicide in Utah than from car accidents.

In 2008, psychiatrist and neurobiologist Perry Renshaw moved to Utah from Boston, where he had worked at Harvard University studying the differences in brain chemistry of depressed people. When he arrived, the suicide rates in his new home made him wonder: Was there something about the elevation that was affecting the way the brain functioned?

His theory didn’t catch on until he and his colleagues published a 2011 paper that looked at all 2,584 counties in the U.S. and found a correlation between average altitude and suicide rate over the previous 20 years. They found that if a county was below 2,000 feet, their suicide rates were about half of counties at 4,000 to 5,000 feet. The counties with the highest suicide rates were above 9,000 feet.

“We got taken much more seriously at that point in time and we were off to the races,” Renshaw said.