A recent report in the Journal of the American Medical Association provided news that didn’t come as a surprise, but on the surface seems counterintuitive. Life expectancy in the wealthiest nation on earth has been declining for the past several years.

Yes, despite all the technology and medical breakthroughs available, Americans are living shorter lives these days, on average, than just a few years ago. In 2014, the average life expectancy in the U.S was 78.9 years. By 2017, it had fallen to 78.6 years.

OK, that’s hardly a huge drop, but to understand the significance, one must understand the terms and the context. First, the historical context: Prior to 2015, life expectancy in the U.S. had risen every single year since the great flu pandemic of 1918. Through World War II, Vietnam and AIDS, we continued to, on average, live longer every year.

The same is true elsewhere, and this is a key finding: The United States is the only developed nation in which people are living shorter lives. Everywhere else, the trend continues upward, though slowly.

As for what “average life expectancy” means in real terms, the gist is simple: We’re living shorter lives, on average, because more of us are dying at a younger age. U.S. mortality rates, especially among those 25 to 65, are way up in the last decade. Again, that’s not really surprising — but it is alarming.

“It’s supposed to be going down, as it is in other countries,” Steven Woolf, the study’s lead author, told The Washington Post. “The fact that that number is climbing, there’s something terribly wrong.”

But what?

The easy answer for some might be the opioid epidemic. The bulk of its victims fall into that age range — admittedly a broad range in any case. It’s a fairly recent development. It’s been claiming tens of thousands of lives for the past 15 years or so.

The same might be said of the rise in suicides nationwide, however. And what of obesity? We know from previous studies that condition is taking a toll on millions of Americans’ health. Surely it must account for many thousands of shortened lives.

The study’s authors cite all of these factors, and more. There’s the rise in distracted driving since smartphones and in-car informational screens became common. Though that’s not showing up in the fatality rate of drivers and passengers — as vehicles are also becoming safer — it is leading to more pedestrian and bicyclist deaths.

The Washington Post report also included this nugget: The mortality rate of those age 25 to 65 is rising fastest right here in the Granite State. The rate of deaths in that range rose more than 23 percent between 2010 and 2017. Nationally, that increase was only 6 percent.

Much attention has been paid to the state’s graying population. New Hampshire ranks second in average age, behind only Maine. But we rank only 37th in the percentage of our population that’s 65 or older. What’s driving the silver tsunami here is that young people have, until very recently, been leaving in droves, while the population of those age 40 to 65 has blossomed.

And while New Hampshire is among the most-affluent states — though it may seem unfathomable to many in this region, a report released just last week put the state’s median family income at $93,930, sixth highest in the country — there is clearly some disconnect or dissatisfaction at work. Opioid deaths and suicides, together dubbed “deaths of despair” in a 2017 Princeton report, have risen dramatically here.

“There’s something more fundamental about how people are feeling at some level,” Ellen Meara, a professor at the Dartmouth Institute for Health Policy and Clinical Practice, told The Post. “Whether it’s economic, whether it’s stress, whether it’s deterioration of the family, people are feeling worse about themselves and their futures, and that’s leading them to do things that are self-destructive and not promoting health.”

In other words, they’re not happy, or optimistic. They’ve given up — or, at the very least, no longer care enough to take care of themselves.

That’s a very bad trend indeed. What to do about it? For starters, efforts to bring the opioid crisis under control must continue, since addiction, for many, is stronger than their sense of self-preservation.

Also, mental wellness must be made more of a priority, included fully in health coverage and policy. More of us need help coping with the stressors and triggers in modern American life. And those with chemical or physiological issues are especially vulnerable.

Lastly, put down the cellphone in the car. Better yet, get out and be one of those pedestrians or cyclists, and you’ll be in better shape for the long haul.