The focus on black adolescents is significant. In much of this research, white Americans appeared somehow to be immune to the negative health effects that accompany relentless striving. As Dr. Brody put it when telling me about the Pittsburgh study, “We found this for black persons from disadvantaged backgrounds, but not white persons.”

Dr. Brody, who does much of his work in African-American communities in rural Georgia, focuses on people who overcome the odds to prosper, academically, professionally and financially. The personality trait that predicts this kind of success against the odds is known in psychology as resilience. Many consider it desirable. Dr. Brody’s summary of the classical tenets of resilient strivers sounds like something from a motivational poster: “They cultivate persistence, set goals and work diligently toward them, navigate setbacks, focus on the long term, and resist temptations that might knock them off course.”

In the United States, gaps in health and longevity between the wealthy and the poor are some of the greatest in the world. It seems natural to assume that jumping from one stratum to the next — being upwardly mobile — would come with gains in health. And conceivably it could work that way — like if a person won the lottery or achieved overnight fortune from writing a truly insightful tweet. But decades of research show that when resilient people work hard within a system that has not afforded them the same opportunities as others, their physical health deteriorates.

The effect has become known as John Henryism. The term was coined by a young researcher named Sherman James in the 1980s, after he met a man named John Henry Martin. Mr. Martin didn’t have any known relation to the John Henry of folk legend who beat a mechanical steam drill in a steel-driving contest, only to collapse dead from exhaustion. (It’s debated whether the original John Henry was himself an actual person with an actual nine-pound hammer that he used to drive metal stakes into Big Bend Mountain in West Virginia in the 1870s so that dynamite could be embedded in the rock and a tunnel could be built for the C.&O. Railroad, or possibly an amalgam of many former slaves who transitioned into freedom.)

Mr. Martin was born into a family of North Carolina sharecroppers in 1907. He worked tirelessly to escape the system and, by the time he was 40, owned 75 acres of farmland. But in his next decade he began to suffer from hypertension, arthritis and a severe case of peptic ulcer disease that required the removal of nearly half his stomach. As Dr. James saw it, John Henry Martin both won and lost his battle with the machine.