So far, we have no evidence that the killers were directed by a terrorist organization overseas or that they were part of a broader conspiracy here at home. But it is clear that the two of them had gone down the dark path of radicalization, embracing a perverted interpretation of Islam that calls for war against America and the West.

In Sunday night’s televised address, President Barack Obama claimed that the threat of terrorism “has evolved into a new phase”—that of home-grown terrorists inspired by ISIS, but not acting at the direction of the ISIS leadership. Although the U.S. military and law enforcement have grown more successful at preventing “complex and multi-faceted attacks like 9/11,” terrorists are turning the “less complicated acts of violence,” such as mass killings. However, when Obama spoke about the steps we are going to take to fight this new threat—more bombing of Syria and Iraq, tighter security, etc.—they turned out to be more of the same policies we have already implemented to fight the old form of terrorism. Maybe that’s why Obama describes desribed this home-grown terrorism—in what may be the most memorable line of the speech—as “a cancer that has no immediate cure.”

The future of Muslim terrorism in this country will depend not only on whether we abandon our seemingly endless war to control Middle Eastern energy resources, but also on social and economic conditions here at home. Home-grown Muslim terrorism has many of the same causes as non-Muslim domestic terrorism. Since 9/11, 48 people have been killed by right wing extremists and 28 by Muslim extremists. Our success in preventing both types of murder will depend on our being able to maintain the loyalty of working class Americans at a time of increasing inequality.

I’ve previously discussed Thomas Piketty’s claim that economic inequality is an important cause of Middle Eastern terrorism. Alvaredo and Piketty attempted to measure the extent of inequality in the Middle East, a task made more difficult by the lack of accurate data. They estimate that the top 10% controls over 60% of Middle East income, while the top 1% controls over 25%. Although the average income in the United States is much higher, income inequality in the U.S. is almost as high as in the Middle East. (In the U.S., the top 1% takes in 23% of the income.) A large body of evidence shows a positive relationship between income inequality and violence. For example, the homicide rate is higher in more unequal countries, and income inequality also predicts differences in the homicide rates of U.S. states. It now appears that our bleak economic conditions are starting to influence the overall death rate.

There has been a long-term decline in U.S. mortality rates, making our lives longer and better. However, Princeton economists Anne Case and Angus Deaton report that between 1999 and 2013, there was a reversal of this trend for non-Hispanic whites aged 45-54. While from 1978 to 1998, the mortality rate for this group declined by about 2% per year, since 1999, it has been increasing by about .5% per year. This translates into 96,000 more deaths than if the mortality rate were flat, and almost 500,000 more deaths than if it had continued its 2% per year decline. Described by the authors as a surprise, this startling increase in deaths has received little attention from the corporate media (although I suspect life insurance companies are on red alert). The closest recent parallel is the increase in deaths in Russia after the fall of the Soviet Union. As Joe Biden might say, “This is a big f***ing deal!”

The reversal is specific to this middle-aged whites. Mortality rates for blacks, Hispanics, and older whites continued to decline. The mortality rate for Hispanics aged 45-54 (262 per 100,000) is lower than that of middle-aged whites (262 v. 415 per 100,000) and declined by 1.8% over the 14 year period. The mortality rate for middle-aged blacks is higher (582 per 100,000), and declined at a rate of 2.6% per year. (To put this in perspective, middle-aged whites now die 71% as often as middle-aged blacks, compared to 56% as often 14 years ago.)

The increase in mortality among middle-aged people is also specific to this country. The graph below compares U.S. whites to the same age group among U.S. Hispanics and the residents of six other industrialized countries. (Both the authors of the study and the New York Times chose to include U.S. Hispanics in this table, but not U.S. blacks. If they had included blacks, of course, they would have needed a much larger graph.)

This is largely a story about social class. Since they didn’t have income data, the authors used education as a substitute. The change was most pronounced among those with a high school education or less. Mortality in this subgroup rose by 22% over the 14-year period, while it remained stable among those with some college and declined for those with a college degree.

The immediate cause seems to be an increase in self-destructive behavior. The change is explained almost exclusively by increases in three causes of death—suicide (up 78%), accidental drug and alcohol poisoning (up 400%), and cirrhosis and other chronic liver diseases caused by alcoholism (up 46%). These folks are committing either rapid or slow suicide.

There was also an increase in morbidity, or poor health, in this subgroup. The percentage reporting themselves in good health declined, and more people reported chronic pain, serious psychological distress, and difficulty in carrying out the activities of daily life, such as walking or socializing with friends. This is consistent with reports of increases in white, middle class drug overdoses caused by overuse of pain medication. (Ironically, the increase in opiate addiction among whites may lead to a more humane drug policy.) Self-reported alcohol consumption also increased. The increased mortality is not explained by obesity, since it occurred at about equal rates for obese and non-obese people.

Case and Deaton attribute these changes to the decline in the standard of living and increasing economic insecurity among middle-aged whites. Deaton suggested in an interview that whites have “lost the narrative of their lives”—that is, they must face the reality that they are unlikely to have a financially secure retirement. A non-college graduate who was 50 in 2013 was born in 1963, and entered the work force around 1981, just about the time that the American corporate class began its relentless assault on the living standards of middle class Americans. The real median hourly wage for white men with no more than a high school diploma declined from $19.76 in 1979 to $17.50 in 2014. The Pew Research Center reports that the percentage of Americans in the middle class, defined as an income between two-thirds and double the national median ($42,000 to $126,000 for a family of three), has declined from 61% in 1971 to 50% in 2015.

Of course, some of these economic trends have occurred in other developed countries as well, but the U.S. has a less adequate social safety net and has neglected its infrastructure. Case and Deaton note that most workers in the U.S. have been forced into defined-contribution retirement plans, while in other industrialized countries, defined-benefit plans are the norm. Defined contribution 401(k) plans shift all of the risk of stock market losses onto the employee. The average wealth of middle-income families declined from $161,000 in 2007 to $98,000 in 2010, where it still stands today.

I realize Case and Deaton have documented distress among middle-aged whites, while terrorists, both white Christian and Muslim, are usually (but not always) younger. My argument assumes that increasing mortality among 45-to-54-year-olds is a cumulative result of economic stress that began at an earlier age, and that anxiety about the future is spreading to younger generations. For example, a poll by Harvard’s Instiute of Politics found that 48% of 18-to-29-year-olds believe that the “American dream” is “dead,” while 49% think it’s “alive.”

Needless to say, terrorism is not the only way inequality contributes to a more dysfunctional society. Research is badly needed on the relationship between economic stress and acceptance of the appeals of fascist demagogues. As Harold Meyerson points out, the increase in the death rate and the rise of Donald Trump “share some common roots: a sense of abandonment, betrayal and misdirected rage.”

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