It was around 9 p.m., a few weeks into the six-month study, when the question popped up on Ms. Cruz’s phone: “Right now how strong is your desire to kill yourself?”
Without stopping to think, she dragged her finger all the way to the end of the bar: 10. A few seconds later, she was asked to choose between two statements: “I am definitely not going to kill myself today” and “I am definitely going kill myself today.” She scrolled to the second.
Fifteen minutes later, her phone rang. It was a member of the research team calling her. The