The roots of this trauma may be, in part, cultural. Most people recognize at an intellectual level that death is inevitable, says Virginia Lee, a nurse who works with cancer patients. But “at least in Western culture, we think we’re going to live forever.” Many of Lee’s advanced-cancer patients tell her they had thought of death as something that happened to other people—until they received their diagnosis. “I’ve heard from cancer patients that your life changes instantly, the moment the doctor or the oncologist says it’s confirmed that it is cancer,” she says.

The shock of confronting your own mortality need not happen at that instant, Coyle notes. Maybe you look at yourself in the mirror and suddenly realize how skinny you are, or notice that your clothes no longer fit well. “It’s not necessarily verbal; it’s not necessarily what other people are telling you,” Coyle says. “Your soul may be telling you, or other people’s eyes may be telling you.”

E. Mansell Pattison, one of the early psychiatrists to write about the emotions and reactions of dying people, explains in The Experience of Dying why this realization marks a radical change in how people think about themselves: “All of us live with the potential for death at any moment. All of us project ahead a trajectory of our life. That is, we anticipate a certain life span within which we arrange our activities and plan our lives. And then abruptly we may be confronted with a crisis ... Whether by illness or accident, our potential trajectory is suddenly changed.”

In this crisis, some people feel depression or despair or anger, or all three. They grieve. They grapple with a loss of meaning. A person’s whole belief system may be called into question because “virtually every aspect of their life will be threatened by changes imposed by the [disease] and its management,” Lee has written. In a small 2011 Danish study, patients with an incurable esophageal cancer reported that after their diagnosis, their lives seemed to spin out of control. Some wondered why they had received a fatal diagnosis, and fell into despair and hopelessness. “I didn’t care about anything,” one patient said. “I had just about given up.”

In the 1970s, two Harvard researchers, Avery Weisman and J. William Worden, did a foundational study on this existential plight. Newly diagnosed cancer patients who had a prognosis of at least three months were interviewed at several different points. At first, for almost all the patients in the study, existential concerns were more important than dealing with the physical impacts of disease. The researchers found that the reckoning was jarring, but still relatively brief and uncomplicated, lasting about two to three months. For a few patients, the crisis triggered or created lasting psychological problems. A few others seemed to face the crisis, then return to a state of denial, and then double back to the crisis—perhaps more than once. In the study, the researchers describe a patient who was told her diagnosis, only to report to interviewers that she didn’t know what it was—and then make it clear she wasn’t interested in receiving a diagnosis in the near future.