You probably already know too much screen time can make you fat and unhappy, but science says that's not actually the worst effect all of our gadgets might be having on our health. Connecting more virtually and less in real life might be literally killing you, dramatic new science warns.

That's not because sitting all day is bad for your health (it is, but it's pretty easy to reverse those effects with just a little movement). That's because our digital lives are part of what's making us increasingly lonely. And according to the latest research, loneliness is even more deadly than a pack-a-day smoking habit.

On cigarettes and screens

It's not that we don't have friends these days. Check your Facebook page. You probably have hundreds. The problem is that we don't often actually see those friends face to face, as the Boston Globe's Billy Baker discovered when his editor asked him to write about the health effects of loneliness recently.

He began reflecting on his own friendships. "First of all, there was my buddy Mark. We went to high school together, and I still talk to him all the time, and we hang out all the . . . Wait, how often do we actually hang out? Maybe four or five times a year?" he writes. "And then there was my other best friend from high school, Rory, and . . . I genuinely could not remember the last time I'd seen him. Had it already been a year? Entirely possible."

If you're navigating the many struggles of middle age, Baker's plight probably sounds entirely familiar. But who cares, right? Maybe it's a bummer that you're too busy to see your friends, but it's hardly a tragedy. Except it just might be. An ever growing pile of studies shows that a lack of face to face time with your fellow human beings will kill you as surely as fast food or cigarettes.

"Beginning in the 1980s... study after study started showing that those who were more socially isolated were much more likely to die during a given period than their socially connected neighbors, even after you corrected for age, gender, and lifestyle choices like exercising and eating right. Loneliness has been linked to an increased risk of cardiovascular disease and stroke and the progression of Alzheimer's. One study found that it can be as much of a long-term risk factor as smoking," Baker uncovers.

A simple way to add years to your life

If you're starting to feel depressed by all this, don't give up hope. The good news is that while loneliness will hasten your death, you don't need to take drastic action to reverse the effects of isolation. Something as simple as hanging out face to face with friends can have a seriously large impact on your health -- and ultimately your longevity.

In her new book The Village Effect psychologist Susan Pinker lays out the case for the near miraculous health benefits of regular, real life social interaction. She recently boiled down her findings for the Guardian, and the article makes for fascinating reading.

From cancer and stroke survivors to super agers in Sardinian villages and your average modern day citizen, wherever scientists look they seem to find huge benefits from actually looking another person in the eyes, Pinker reports. "When the daily habits of nearly 17,000 utility workers in France were monitored throughout the 1990s, researchers discovered that their degree of social involvement was a good way to predict who would still be alive at the end of the decade," she claims, for example.

Your friends are basically a wonder drug, in other words, but the sad part is many of us are missing out on the benefits of social interaction. "Despite evidence that confirms the transformative power of social contact, our routines have become more solitary," Pinker notes. "Since the late 80s... the number of people who say they feel isolated has doubled if not trebled, according to population surveys in Europe, the US and Australia."

The bottom line for the average overscheduled, screen addled adult is twofold. One, your failure to get out as much as you like isn't just a minor nuisance. You're isolation is literally hastening your demise.

The second takeaway, however, is more cheerful. Just as it's easy to slip into a solitary life, it's way easier to break this bad habit than it is to quit cigarettes or lose a few dozen pounds. Unlike giving up chocolate cake, meeting friends is actually pleasurable, after all. Make it a priority and you'll not only be happier, you'll also add years to your life.