Since the turn of this century, death rates have risen for whites in midlife, particularly women. In this series, The Washington Post is exploring this trend and the forces driving it. Read the entire series.

While death rates are falling for blacks and Hispanics in middle age, whites are dying prematurely in growing numbers, particularly white women. One reason: a big increase in overdoses, primarily from opioids, but also from anti-anxiety drugs, which are often prescribed in tandem.

Between 1999 and 2014, the number of middle-aged white women dying annually from opiate overdoses shot up 400 percent, according to a Washington Post analysis of data from the Centers for Disease Control and Prevention. Anti-anxiety drugs known as benzodiazepines contributed to a growing share of the 54,000 deaths over that period, reaching a third in the last several years, The Post found, though spotty reporting in death records makes it likely that the combination is even more widespread.

Both drugs depress the central nervous system, temporarily easing pain and anxiety while suppressing respiration, heart rate and the gag reflex. Alcohol has the same effect, and combining any of these can be fatal.

“They act like a dimmer switch on the central nervous system,” said Rear Admiral Susan Blumenthal, former U.S. assistant surgeon general and an expert on women’s health issues. “When taken in combination, a person’s breathing and heart will slow down, and can ultimately stop. People can go to sleep and never wake up.”

White women are more likely than women of other races to be prescribed opiates, and far more likely to be prescribed both opiates and anti-anxiety drugs, according to a Post analysis of middle-aged participants in the latest National Health and Nutrition Examination Survey. White women prescribed opiates are five times as likely as white men to be given that drug combination — helping to explain why white women may be at special risk.