Feeling lonely? Your brain may process the world differently

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The U.S. is in the midst of a loneliness epidemic.

For a lot of people, the feeling is even more pronounced during the holidays.

In addition to the emotional impact of chronic loneliness, it has some dramatic health consequences: increased risk of heart disease and stroke, infections, cancer, even death.

Recent research also suggests that loneliness can change the way the brain processes the surrounding world.

What is loneliness?

Generally, researchers define loneliness as the subjective feeling of social isolation. People may feel lonely when their social needs are not met by the people around them.

Loneliness can have more than one cause.

Laetitia Mwilambwe-Tshilobo, a social cognitive neuroscientist at Princeton University, says "loneliness" captures two distinct groups:

• people with a low number of social connections
• people who feel they have poor quality existing relationships

This stands in contrast to multiple papers Mwilambwe-Tshilobo says she noticed that put forward a single depiction of what loneliness looks like in the brain.

"It was hard for me to reconcile this idea that we had this very specific characterization of ... the changes or the differences between lonely and not lonely people — in terms of the cognitive changes, their behavioral changes and brain changes," Mwilambwe-Tshilobo says. "But we had this definition that encompassed two seemingly different groups of individuals."

Lonely people may process the world differently

Elisa Baek is a social neuroscientist at the University of Southern California studying the basis of social interaction. This year, she co-authored a study that looked at whether lonely people view the world differently than non-lonely people, specifically among college freshman. The research was published in the journal Psychological Science.

She and her collaborators found that while non-lonely people were all similar in their neural responses, lonely people had responses that were really different – not just from the non-lonely group, but also from each other.

Baek says that these idiosyncrasies in how lonely participants process the world, "may pose challenges in how people ... are able to achieve social connection and feel connected with others."

To study these changes to the brain, Baek and her collaborators collected fMRI data – a measure of blood flow changes in the brain – while first-year college students watched short videos to measure how similarly participants' brains responded to the videos. The videos ranged from dramatic and comedic clips to instructional demonstrations in order to mimic scenarios participants might experience in daily life. She says it's the closest they could get to studying people's brain activity — and how they process the world — while they were going about their lives.

The main area where researchers saw these effects was a group of brain regions called the default mode network.

The default mode network includes areas of the brain involved in higher-order cognition. The region is thought to be involved in meaning-making, or integrating experiences of the external world into internal information, like past memories and knowledge. It's particularly involved in social cognition, or how we think about others.

"So this is the system that's thought to be important in kind of determining how we process, understand and react to what's happening around us," Baek says.

Mwilambwe-Tshilobo, who is unaffiliated with the study, says the research highlights the individual nature of loneliness.

"What that study does very beautifully is really capture this idea that loneliness isn't just one concept to kind of capture all of the lonely people, but that we really need to start thinking about how there are individual differences in how people experience loneliness," she says.

Scientists do see some patterns in the brains and behavior of people who experience loneliness. For example, research shows lonely people may pay more attention to negative social cues than people who are not lonely.

But Baek says her team's study is one of the first to look at the differences in lonely and non-lonely people's brain responses to stimuli.

The future of loneliness research

Whether people who are lonely already have different brains than people who are not or if chronic loneliness changes the brain remains to be seen.

Baek and her team are working on studies that will try to answer it by following participants and tracking brain data over the course of years.

In the meantime, Baek and Mwilambwe-Tshilobo both say one salve for feeling lonely may be to double down on building the strength of a person's connections rather than increasing the overall number of friends or relationships.

"Trying to connect more deeply with one or two or three other people may be more important than to try to get to know everybody and being good terms with everybody," Baek says. "And it doesn't have to be someone who is like-minded with you. It's more like: How can we get on the same page with people who we might not start off on the same page with, but that might form deeper connections?"

Mwilambwe-Tshilobo suggests trying activities where someone might bump into people with similar interests — like taking an art class or going to a concert.

"It doesn't have to be something super complicated," she says. "It could just be reaching out and saying hello."

Curious about human behavior? Email us at shortwave@npr.org.

Listen to Short Wave on Spotify, Apple Podcasts and Google Podcasts.

Today's episode was produced by Berly McCoy. It was edited by Rebecca Ramirez. Brit Hanson checked the facts. Patrick Murray was the audio engineer.