ProPublica and NPR just dropped an astonishing piece by Nina Martin and Renee Montagne about health disparities in pregnancy between black and white women. The key stat is this:

The disproportionate toll on African Americans is the main reason the U.S. maternal mortality rate is so much higher than that of other affluent countries. Black expectant and new mothers in the U.S. die at about the same rate as women in countries such as Mexico and Uzbekistan, the World Health Organization estimates.

What's more, black women with relative social and economic advantages, such as a college degree, have been found to have considerably higher risks in pregnancy than white women without such advantages, which is why they base their analysis around one woman—the daughter of Dartmouth grads, a brilliant epidemiologist with two Ph.Ds who literally studied the long-term effects of childhood circumstances on long-term health outcomes—died at the age of 36 after a pregnancy. Which is why the title of the piece is "Nothing Protects Black Women From Dying in Pregnancy and Childbirth: Not education. Not income. Not even being an expert in racial disparities in health care."

One of the possible causes they explore is, quite simply, racism. It causes stress, which causes the body to age, even at the cellular level—what one researcher calls "weathering."

It's an idea that's emerged in recent years, and is the subject of considerable amounts of study. And one of the loci of that study is Chicago. I've written about this before; for example, a study of race and sleep, which found that in Chicago, whites get about half an hour more sleep per night than African-Americans, Asians, or Hispanics, and tend to fall asleep faster and sleep better. That number is comparable to other findings—one University of Chicago epidemiologist found the difference was about an hour between blacks and whites, another large-scale recent study found a difference of about 45 minutes.

A very recent study led by Northwestern's Mercedes Carnethon landed in the same ballpark: a difference of 40 minutes. Carnethon and her colleagues then looked at cardiovascular complications like stroke and hypertension, and found that they could explain "more than one-half of the racial disparities in cardiometabolic risk" as a result of sleep differences. Furthermore, they found an indirect association between race, sex, sleep, and disease risk only among women—a tendency reflected in the general literature. Similarly, another recent study out of Northwestern looked at the correlation between self-reported discrimination and specific indicators of inflammation, and found associations for women but not for men.

Researchers are puzzling out how this works. There's considerable evidence that this stress does damage within the body all on its own, but there's also evidence that coping mechanisms can play a role. James Jackson, a social psychologist at the University of Michigan, came to the University of Chicago for a seminar series on health disparity to present an intriguing theory about depression, coping, and health, building off a paradoxical observation: African-Americans tend to have worse health outcomes than whites, but lower rates of depression. It's an even more paradoxical finding the more we learn about the prevalence of stress.

Jackson's explanation is intuitively simple and familiar. After all, almost everyone knows how feelings of stress and depression can be ameliorated with various consumables. So he suggested that the racial gap—18 percent of whites are diagnosed with depression compared to 10 percent of African-Americans and Caribbean blacks—may be the result of seeking diagnosis versus self-medication. He tested this by looking at the exceptions that might prove the rule:

Jackson’s group found that African-Americans who engage in fewer unhealthy coping strategies (smoking, drinking, or drugs) actually have higher rates of depression, while those who do use eating or drug use to cope with these behaviors have the lower rates reflected in the broader black population. It’s a perverse trade-off, he said.

“Blacks and other groups in society may ‘buy’ their reduced rates of psychiatric disorders, with higher rates of physical morbidities and early mortality,” Jackson said.

This idea might lead some to wonder whether disparities could thus be explained by biological differences in the stress pathway of blacks and whites. But Jackson disagrees with the idea of race as a variable that influences stress response, instead arguing that a stressful life “racializes” individuals in a society where disadvantage is so closely linked to race. In one experiment, Jackson tried to make “white people black” by looking at whites who encountered similar stress variables (i.e. poverty and living conditions) over their life as the average black person in America. Here he found the same trade-off between coping behaviors and mental health: the more unhealthy coping behaviors used, the lower the risk of depression. So the stress produced by a lifetime of hardship and discrimination, not biological factors of race, may be the smoking gun of disparities.

That last bit—Jackson's observations about white people being exposed to intense socioeconomic stress—may be increasingly relevant today. One of the more striking findings in public health this decade has been the work of the University of Illinois's S. Jay Olshansky, who found that the lifespans of white female high school dropouts had fallen by five years from 1990 to 2008. No one is really sure why, but in a lengthy investigation for The American Prospect, in which she spoke with both Olshansky and Jackson, Monica Potts concluded that a confluence of factors have made their lives increasingly stressful. As the above studies suggest, stress can kill through coping mechanisms, or it can kill on its own.

In 2008, Olshansky found a remarkable increase in coronary artery disease in Olmsted County, Minnesota, a 90-percent-white county in the southeastern corner of the state, by examining autopsy findings from 1980 to 2004. In the last four years of their sample, those disease rates shot up after two decades of decline. Then, Olshansky called it "the canary in the coal mine." When I interviewed him in 2015, he told me that "the canary in the coal mine has died."

What can be done? The stressors are many, but another recent study, out of the University of Georgia and Northwestern, found something interesting. They examined young African-Americans for self-reported instances of racial discrimination between the ages of 17 and 19, and levels of inflammation at the age of 22. They found greater inflammation among those who reported high levels of discrimination—the kind of inflammation that causes premature aging, or "weathering." But among the youth who "embraced positive views and rejected negative stereotypes” about their racial identity, they found no significant association.