Loneliness is epidemic, and in the coming years it could explode.

Forty percent of people age 65 and older report being lonely at times. And the percentage of people living alone has been rising steadily since the 1960s.

Look at this GIF of how America will age until 2050. It's a wave of increasing old age, but it may also represent a soul-crushing wave of loneliness as baby boomers age into their 70s.

Humans are social creatures; our entire psychology is built on coexisting with each other. Social relationships guide our decisions to join groups, go to war, gain status, empathize, punish, marry, and mate. Having evolved this way means we suffer without the companionship of others.

"What studies also show is that [loneliness] has real physiological consequences," says Maike Luhmann, a psychologist at the University of Cologne in Germany. "Blood pressure goes up, and it can go up permanently. You can see these mechanisms then lead to more general health problems in people. And in the end, it makes them die earlier."

A 2015 meta-review of 70 studies found loneliness increases the risk of mortality by 26 percent . "The risk associated with social isolation and loneliness is comparable with well-established risk factors for mortality," like obesity, substance abuse, and mental health, the study reported. "Some say loneliness has the same effect on longevity as smoking," Luhmann says.

Though loneliness is most acute in old age, Luhmann is finding new evidence that it doesn't spare the young. The feeling might naturally peak and dive over the course of our lives in a predictable way.

"Around 30, there’s elevated levels of loneliness, and then again at age 50," Luhmann says. That's what she saw in a study of 16,000 Germans recently published in Developmental Psychology. "That has not been found before."

"However old you are, it’s always a good idea to make friends. ... That’s the best thing you can do to not become lonely"

It's depressing, but there's also plenty of reason for hope. As Luhmann recently told me by phone, it doesn't take that much to stay connected with others and make a difference.

The following conversation (of our phone call and some follow-up emails) has been edited for length and clarity.

How loneliness can be a good thing

Brian Resnick: What is loneliness?

Maike Luhmann: Humans are a social species. We really depend on having social connections. And most of us suffer when we don’t have them — not all of us, but most of us.

Some people are alone most of the day or live alone somewhere out in the desert, and they might be okay with this. Being alone is not the same as feeling lonely. Loneliness is feeling one has fewer meaningful social connections than one might like to have.

For some people, this might mean they have one meaningful connection and they are fine. For others, it might mean they need 10. It’s really different from person to person.

That’s why we can’t really look at the number of friends a person has. Are they married? These objective things don’t tell us how lonely a person might be.

Loneliness really hurts. It literally hurts. Brain studies show that the same areas in the brain light up when you experience social pain as when you experience actual physical pain.

BR: How do you measure loneliness?

ML: There are two ways. One is asking, "How often do you feel lonely?" But there’s a problem with using the word lonely, because there’s a stigma. Even people who do feel lonely might not admit it, not even to themselves. What we did in our study was that we had more indirect questions, like, "Do you feel connected to others?"

"When we feel lonely, we feel like there’s a permanent threat. It might not be a real threat, but we perceive things as threatening."

BR: Everyone feels lonely every now and again. Is that problematic?

ML: It’s completely normal for every one of us to feel lonely at times in our lives. Everyone has felt lonely. That’s not a bad thing. It’s actually a good thing.

BR: Really? Loneliness can be a good thing?

ML: As long as we then do what we should do — reconnect with people — then loneliness is a good thing. It signals that we need to do something about our social connections. This is a sign from our psychological systems that there’s something off.

It becomes a bad thing when it becomes chronic. That’s when the health effects kick in. And it becomes harder and harder to connect with other people the longer you are in the state of loneliness.

Loneliness can become a vicious cycle

BR: That's so tragic. Why does it become harder to connect the longer you are lonely?

ML: There’s an interesting theory.

We depend on others to feel secure. When we feel lonely, we feel like there’s a permanent threat. It might not be a real threat, but we perceive things as threatening.

So what this amounts to when we’re in a normal, neutral social situation, we’re more likely to interpret the other person as being threatening. Someone might look at us in a neutral way, and the lonely person will think, "This person doesn’t like me."

BR: That sounds like a hard cycle to break.

ML: It is very hard. So if I perceive my surroundings as hostile, and I become unfriendly, then other people withdraw. Then my subjective loneliness becomes objective isolation.

Being aware is probably a first step out of the cycle.

BR: Are there people who never get lonely? Is something wrong with them?

ML: There probably are some people who never get lonely, no matter the circumstances. I am not aware of any research that studies these kinds of people, possibly because it would be necessary to track the same people over long periods of time.

People do differ in how much social contact they need and desire.

How extroverted someone is may explain why some people feel lonely when they are alone and others feel just fine when they are alone. People also differ in what kind of social relationships they desire. For some, it is of fundamental importance to have a romantic partner, and they feel lonely if they are single no matter how many friends they have. Others do not care for romantic relationships as much and are therefore fine when single.

Loneliness may naturally ebb and flow throughout our lives

BR: In your recent study of 16,000 Germans, you found evidence that average levels of loneliness peak and dive over the course of life. And that loneliness in midlife may be more common than most realize. Can you explain this pattern?

ML: First, what we find is that in old age, after 80, we see a substantial increase in average levels of loneliness. That’s not surprising. Others have found this too.

What’s interesting is that before old age, we found differences over adulthood.

Around 30, there are elevated levels of loneliness, and then again at age 50. Or, to frame it another way, there’s a dip in loneliness around age 40, and then again around age 65 to 70.

And that’s quite interesting because that has not been found before. We don’t quite know why this is happening. So most of the previous research has focused on old age, and for good reason, because it's when loneliness levels are high.

But researchers have ignored that loneliness can happen at any time. And there seem to be certain times or certain age groups when it’s more common.

BR: This is a snapshot study of people at one point in time. Could the effects just be generational, that 30-somethings are just a lonelier generation?

ML: That is a very good point, and one of the most important limitations of our study. These effects might be generational. We need longitudinal data covering multiple years and several generations to figure out to what extent the age differences we observed are due to aging or to generational differences.

BR: Is there any chance this pattern only applies to Germans?

ML: The pattern seems to be specific to Western countries. We’re doing some analyses with American data, and we find a pretty similar pattern. We find that in old age, loneliness goes way up, but there are also elevated levels earlier in life. Those results tell us probably it’s generalizable. (But this is not even submitted for publication yet.)

"That health matters is something we should remember when people are in poor health. We should still look out for them and make sure they don’t become disconnected"

BR: Why might we be more prone to loneliness during certain periods of life?

ML: We have surprisingly little [to explain this].

You could imagine those around 30, they have their first child, and that could make them more lonely because they’ll have less time for their friends. And those around 50 might be lonely because their children have left and they’re home alone. But we didn’t find any evidence for either.

When we control for children, it doesn’t change. It explains some of the difference [between people], but it doesn’t change the pattern. So that’s one thing.

We tried things like income, health, or whether they lived alone or with other people, whether they had work or not.

All of these things explain individual differences in loneliness, but they do not explain why people at certain ages are more or less lonely than other ages. The only thing that explains is old age.

BR: Something like a midlife crisis, then?

ML: Maybe. We weren’t able to explain it. It’s really an open question.

BR: I guess, at least, it shows that loneliness can strike all throughout life. And if you're feeling lonely, you're not alone with those feelings.

In your paper, you bring up an interesting speculation — that the fluctuation is because the criteria for loneliness may change as we age.

ML: We were thinking along the lines of what is important at different ages. When you’re a young adult, you have these developmental tasks. You have to find a partner. Maybe get married, have kids. At the same time, find a job, start a career — all these things people are supposed to do in this age period. This means that specific social relationships might be more important at certain life periods than others.

BR: I liked this line in your paper: "For instance, a teenage girl may feel lonely if she has only two good friends, whereas an 80-year-old woman may feel very connected because she still has two good friends."

ML: That’s something that we mentioned, but we actually found the number of friends matters equally across the life span.

But there's hope: Friendships matter

BR: What's the best way to avoid loneliness?

ML: In general what matters is social connection, social relationships. It might seem obvious, but it is a fact that the more friends you have and the more frequent contact you have with them, the less lonely you will be.

Health is also a big predictor.

Loneliness protects health, but it’s really a bidirectional. So health also affects loneliness. When you’re in poor health and you cannot leave the house and you can’t walk well, or if you have some other limitations, then you will have less contact and you will be more lonely than others.

Number of friends, how often you talk to a neighbor — these things really matter equally across the life span, but there are some risk factors that are more important in certain periods than others. Whether you work is more important in young and middle adulthood than when you retire.

That health matters is something we should remember when people are in poor health. We should still look out for them and make sure they don’t become disconnected. It’s hard for them. It might be easier us to prevent that.

BR: Do you have any ideas on how we can better combat the loneliness epidemic in older people?

ML: Loneliness needs to be battled on multiple levels.

As family members, we can watch out for signs of loneliness in our older relatives and try to help them. We know from our research that functional limitations are a common source of loneliness among older people. As relatives and friends, we might be able to provide very practical support, such as driving our grandmother to her favorite events when she can no longer drive herself.

I think it is also important to generally make people aware of the negative health consequences of loneliness. For instance, in the United States, many retirees move to Southern states where the sun always shines but their family and friends are far away. This might not always be a smart move from a health and psychological perspective.

The first step is to become aware, as individuals and as a society, that loneliness is quite common in older people and is a serious health problem.

[Note: There are organizations devoted to decreasing loneliness in old age.]

BR: What's the most important takeaway you think people should learn from loneliness research?

ML: However old you are, it’s always a good idea to make friends and stay in touch with your friends. That’s the best thing you can do to not become lonely.