For much of his thirties, Jesse Bering thought he was probably going to kill himself. He was a successful psychologist and writer, with books to his name and bylines in major magazines. But none of that mattered. The impulse to take his own life remained. At times it felt all but inescapable. Bering survived. And in addition to relief, the fading of his suicidal thoughts brought curiosity. Where had they come from? Would they return? Is the...