For years, Rocky Mountain states have had a higher suicide rate than the rest of the nation. The question as to why Colorado, Utah, New Mexico, Montana, and Nevada are consistently among the top 10 states in terms of suicides now has one intriguing answer: the mountains, and specifically, the accompanying higher elevation. That’s according to ABC News, which cites research suggesting that people who already have mental health issues may become more likely to commit suicide if they are living in an altitude with thinner air. University of Utah psychiatrist Perry F. Renshaw says his researchers have analyzed historic data from various agencies and found an “astonishingly strong” connection between higher altitudes and increased suicide rates, highlighted in the latest edition of the American Journal of Psychiatry.

There are typically more suicide deaths in Colorado than automobile accidents, according to Boulder’s Daily Camera. While the West’s independent culture, including gun ownership, have often been blamed for the higher rate, Renshaw has found higher rates in higher altitude countries with different cultures—South Korea and Italy.

Dr. Marian Betz, an assistant professor in emergency medicine at the University of Colorado School of Medicine, says the findings are interesting, but “my read is that there are lots of other things that vary at altitude, including access to social services.”