Greater stress and anxiety resulting from economic insecurity may be at least partly to blame for the U.S. death rate that the government announced Dec. 8 has increased for the first time in a decade, says an expert on poverty and inequality at Washington University in St. Louis.

"For the first time since 1993, the overall life-expectancy rate in the United States last year actually went down, according to the Centers for Disease Control and Prevention," said Mark Rank, the Herbert S. Hadley Professor of Social Welfare at the Brown School.

"This was particularly true for those under the age of 65," he said. "This news comes at the exact same time as empirical research from Stanford University demonstrates that over the past several decades, the American Dream has become harder to obtain."

Coincidence? Rank thinks not.

"As the recent election has exposed, more Americans are feeling the pressure of economic insecurity," said Rank, co-author of the influential 2014 book "Chasing the American Dream: Understanding What Shapes Our Fortunes."

"This economic insecurity has led to widespread anxiety within the population, with greater numbers of households struggling to stay afloat," he said. "In short, the hopes and dreams for many ordinary Americans have been getting further and further out of reach."

Therefore, Rank contends, it is important to note that the recent fall in the life expectancy rate "occurred largely as a result of rising levels of heart disease, stroke, unintentional injuries and suicide."

"All of these are closely associated with greater levels of stress and anxiety," he said. "As stress and anxiety goes up, so too does the probability of one of these causes of death."

As a result of several well documented economic trends, including rising income and wealth inequality, America is quickly becoming a society of haves and have nots, Rank said.

"On the one hand, the haves are getting richer while their numbers are getting smaller," he said. "On the other hand, the have nots are becoming poorer while their numbers are growing larger. The result may be the canary in the coal mine -- overall life expectancy in the United States just went down."