The Chilling Mystery of High-Altitude Suicides

U.S. counties above 4,000 feet have twice the suicides as counties at 2,000 feet. Is it because there's less oxygen in the air, or is something else going on?
Read more: https://www.vice.com/en_us/article/xwnpxj/the-chilling-mystery-of-high-altitude-suicides?source=Snapzu