Loneliness can be difficult. Lonely people often feel isolated and sad. Research has been finding that lonely people are more susceptible to diseases, both physical and psychological. Now scientists are discovering where in the brain loneliness is triggered and how loneliness affects the brain.
Dr. John Cacioppo from the University of Chicago says people survive better when they're in groups. He and his colleagues have come to believe that the feeling of loneliness may have actually evolved in humans as a way of telling us when we're too isolated. He says loneliness could actually be like hunger, thirst or pain.
"It's not so much an individual difference. You are either lonely or are a non-lonely person," Cacioppo says. "But rather, it's an adversive signal that has evolved because it protects us. It signals us about a condition that puts us in danger. This is a signal that says, 'Oops, you're starting to get disconnected.'"
Cacioppo did several studies to learn how both lonely and non-lonely people process social signals. First, he gave people a questionnaire asking them how they were feeling - whether or not they felt lonely. Then he showed them photographs of people in happy situations, like couples walking hand in hand, and people in difficult situations, such as fights.
"Lonely individuals saw the positive events as less uplifting, less strong, less rewarding than did the non-lonely individuals," Cacioppo says. "And those negative events... they saw to be more severe hassles."
Then Cacioppo placed his subjects into a scanning machine that can track where blood flows in the brain. While subjects were in the scanner, he showed them photographs and looked at what happened in the parts of the brain that respond to pleasure. The pleasure centers in the brains of lonely people were less active than were the brains of non-lonely subjects. This was especially the case when they looked at photographs of happy people.
Cacioppo says a suppressed pleasure response may partially explain why lonely people are more likely to become ill. He says researchers had previously thought that lonely people became more ill because they were socially isolated.
"There weren't friends or there weren't family members to tell you go take care of yourself... " Cacioppo says. But he says this research on the brain suggests that there is a different process at play.
"Loneliness compromises your ability to regulate yourself, and it has a direct effect on some of the stress systems," he says. "So if you feel lonely, and you feel lonely for an extended period of time… your stress physiology starts to ramp up."
Cacioppo hopes that by learning more about loneliness and how it affects a person's brain and biology, doctors can figure out better ways to help people who feel lonely.
Cacioppo's research is published in the Journal of Cognitive Neuroscience.