But it's been growing for decades.

Loneliness is the sense that I am less connected to other people than I want to be.

It's a very subjective experience and that makes it different too from isolation.

So I can deliberately isolate myself and feel great about that.

But only you can tell if you're lonely.

And the fact is you can be lonely in a crowd, you can be lonely in a marriage.

You can also be very content and not lonely alone on a mountain top.

Starting in the 1950s and going all the way through to today, we know that people have been less and less invested in other people.

In some studies, as many as 60% of people will say that they feel lonely much of the time.

And the lowest estimates are 30 to 40% of people say they feel lonely.

Young adults aged 16 to 24 are the loneliest age group.

And then again, among older adults, there is an increase in loneliness, particularly as people lose friends, lose partners.

But loneliness is pervasive across the world, across all age groups, all income groups, all demographics.

There are so many factors that are responsible for this loneliness epidemic.

They did not just begin with the digital revolution.

Loneliness was on the rise as we know at least from the 1950s.

In part because of social dislocation, we've become a much more mobile society where the networks of family and friends get disrupted as people move for jobs and other kinds of opportunities like education.

All of that is good on the one hand, but that it tears us away from the fabric of belonging that many of us are born into and spend much of our lives creating.

Then there is the world of screens.

So when television came into the American home, there was a decline in investing in our communities.

People went out less, they joined clubs less often, they went to houses of worship less often, they invited people over less often.

All of that seems to contribute to our increasing disconnection and our increasing levels of loneliness.

That was made worse as the digital revolution gave us more and more screens to look at and software that was designed specifically to grab our attention, hold our attention and therefore keep it away from the people we care about.

We know that people with strong social bonds are much less likely to die in any given year than people without strong social bonds.

There's good work by Julianne Holt Lundstedt, who is a researcher who studies loneliness, and what she finds is that loneliness is as dangerous to our health as smoking half a pack of cigarettes a day.

We think that stress is one of the main causes of physical health breakdown that comes from loneliness.

But there are probably other causes as well.

And in addition, the research shows that people who are lonely in late life have more rapid brain decline.

So we know that this same process of increased stress or decreased stress affects how our brains age.

And many other studies show that the single choice we can make, that's most likely to keep us on a good path of well-being is to invest in our relationships with other people.

It's not just our closest relationships that make us feel connected, it's all kinds of relationships.

It's the person who delivers the mail, it's the cashier who checks us out at the grocery store.

It's all these casual encounters.

All of these ways of making it a little bit more personal do a lot to make other people feel like they belong and they make us feel more like we belong.

Many people who are lonely feel that others don't want to be with them.

And what we know is that lonely people can sometimes give off the message that they don't want to be approached because they're afraid of others, they're afraid of the world.

And so it may be that lonely people can learn more about making gestures and giving off signals that say, "I would like to connect," even when they're a little bit afraid to do so.

And so they've actually developed forms of cognitive behavior therapy where people are taught these social skills and taught how to revise their assumptions about not being wanted by other people.

My recommendation, if you're feeling lonely and a little bit afraid is find a setting, find an activity around other people where you are comfortable and see what develops.

You belong, you matter, you're connected.