A mural in West Virginia, where mortality rates are higher than at any time since 1980.

Late last year, a study in the Proceedings of the National Academy of Sciences found that middle-aged, white Americans have been getting sicker and dying in greater numbers, even as the rest of the world is living longer and healthier.

The authors of that study attributed the trend to what we called “despair deaths:” mainly suicides, drug overdoses, and alcohol-related liver disease.

Now, a new analysis from the Commonwealth Fund suggests there’s more to the story. The report, by David Squires and David Blumenthal, notes that between 1999 and 2014, mortality rates in the U.S. rose for white Americans aged 22 and 56. Before that, death rates had been falling by nearly 2 percent each year since 1968. Squires and Blumenthal call the difference between the those two mortality trend lines—the expected, declining one and the actual, rising one—the “mortality gap.”

The Mortality Gap for White Americans, By Age

In 2014, they write, the mortality gap was so big that it accounted for an extra 100 dead, middle-aged white people for every 100,000.

By digging through CDC data, they saw that the reason death rates failed to decline as expected was not entirely due to suicide and substance abuse. Although those factors explained about 40 percent of the gap, the rest was attributable to the leading causes of death—things like heart disease, diabetes, and respiratory disease. Though there are still fewer people dying from those diseases than there were in the 1960s, according to this analysis, the rate of decline has slowed.