Rising drug and alcohol overdoses, suicides, and disease from chronic alcoholism -- labeled "deaths of despair" by one expert -- are cutting the lives of white Americans short by nearly a half a year on average.

Increases in these types of deaths among whites means that life expectancy for whites is not increasing as fast as it is for other groups, according to a government report that offers an unusual look at how different threats are affecting U.S. lifespans.

"Things are moving in the wrong direction," said Anne Case, a Princeton University researcher, of what she calls "deaths of despair."

Drawing from death certificate data, the new report from the Centers for Disease Control and Prevention focuses on what happened to white life expectancy between 2000 and 2014.

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The work was a reaction to recent research that suggested drug overdoses and suicides have caused alarming increases in death rates for middle-aged white Americans. The new report, which did not perform the same analysis for blacks and Hispanics, was posted online Friday.

Overall, white life expectancy still grew because other things were improving. Deaths from heart disease - the nation's No. 1 killer - dropped significantly, and that alone added a year to white life expectancy. Nearly one more year was added because of falling death rates from cancer, stroke, and motor vehicle crashes, the researchers found.

But then drugs and alcohol subtracted about 4 months from life expectancy, according to Kenneth Kochanek, a CDC statistician who was the report's lead author. No other cause of death had a bigger negative impact, he said.

Increasing suicides had the second largest negative impact, subtracting roughly 6 weeks from white life expectancy. The growing impact of Alzheimer's disease was third, reducing longevity by about 3 weeks.

Falls also whittled down white life expectancy gains, the researchers found. So did chronic liver disease, often the result of heavy alcohol consumption or injection drug use that spreads the liver-destroying hepatitis C virus.

Experts cite several possible reasons that drug overdose deaths and suicides are occurring far more often among middle-aged whites than other groups. They say whites have had an easier time getting access to the powerful painkillers that have been the root of the current drug overdose epidemic. And whites may more quickly turn to suicide because often they don't have the kind of family and social support often seen in black and Hispanic communities, they say.

Though the gap is closing, white life expectancy is still significantly greater than life expectancy for blacks.

White life expectancy grew to nearly 79 in 2014, from about 77 ½ years in 2000. Black life expectancy rose to a little over 75 from about 71 ½. Life expectancy for Hispanics rose to 82 years from 79.

Things may be taking a turn for the worse, however. Earlier this week, CDC issued a report on preliminary death data for 2015 that showed the U.S. death rate rose slightly -- the first increase in a decade. The report did not break down what was happening in different racial groups, but experts say whites death trends are likely the primary reason.

"This all just points to the fact that we have a very serious problem that we don't fully understand," Case said.