At first, the stress of combat seemed to be the obvious reason for the jump in military suicides — until researchers realized that the rate has also risen among soldiers who were never deployed. Public-health experts have speculated that the uptick in suicides among the middle-aged is linked to modern tensions like the troubled economy, the stress of caring for elderly parents and insolvent children, and unprecedented access to prescription drugs. Nock, conversely, tends to point to a graph showing how the suicide rate for 45-to-64-year-olds has dipped and risen over a longer period of time — the rate today is similar to what it was 20 years ago. The graph tells a more complicated story. “My thought is that we’ve had theories of suicide for a long time and no data,” he said. “So we want to work from the other end.”

Indeed, Nock has started from scratch by searching for a way to precisely measure suicide risk. Three years ago, he and his team published a paper suggesting that they had found, for the first time, an objective test that could predict a psychiatric patient’s likelihood of a suicide attempt better than the patient or his clinician could. Nock is now running it and other tests on hundreds of people — those who have tried to kill themselves, those who have had suicidal thoughts and those who have not — to see how the initial scores differ from one group to another and whether those scores will end up having forecasted, beyond what current methods can, who will try to kill themselves in the future.

Each data point Nock collects moves him one step closer to his ultimate goal: to be able to give people a series of tests that could tell them — and their psychiatrists or primary care physicians or school nurses — how high their risk of suicide is at any given moment, much the way cardiologists can use blood-pressure and cholesterol readings combined with weight and height to calculate a person’s risk of heart disease.