NEW YORK — 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."