Scientists have now understood that loneliness often affects the way a person behaves and how his or her brain operates; these results have been developed from a study that highlighted the connection between the brain's behavior and social isolation.
The study at the University of Chicago (UC) is the first to use fMRI scans to study the connections between perceived social isolation and activity in the brain.
And by combining fMRI scans with data relevant to social behaviour, UC scientists are pioneering a new approach to psychology, which could be an emerging field for examining brain mechanisms.
In the study, the researchers found that the ventral striatum-a region of the brain associated with rewards-is much more activated in non-lonely people than in the lonely when they view pictures of people in pleasant settings.
On the other hand, the temporoparietal junction-a region associated with taking the perspective of another person-is much less activated among the lonely than in the non-lonely when viewing pictures of people in unpleasant settings.
"Given their feelings of social isolation, lonely individuals may be left to find relative comfort in nonsocial rewards," said John Cacioppo, the Tiffany and Margaret Blake Professor in Psychology at the University.
The ventral striatum, which is critical to learning, is a key portion of the brain and is activated through primary rewards such as food, and secondary rewards such as money. Social rewards and feelings of love also may activate the region.
The researchers have shown that loneliness undermines health, and can be as detrimental as smoking.
For the study, they tested 23 female undergraduates to determine their level of loneliness. However, in an fMRI scanner, the subjects were shown unpleasant pictures and human conflict as well as pleasant things such as money and happy people.
The lonely subjects were least likely to have strong activity in their ventral striata when shown pictures of people enjoying themselves.
Although loneliness may be influence brain activity, the study indicated that activity in the ventral striatum might prompt feelings of loneliness,
"The study raises the intriguing possibility that loneliness may result from reduced reward-related activity in the ventral striatum in response to social rewards," said Jean Decety, the Irving B. Harris Professor in Psychology and Psychiatry at the University.
Apart from differing responses in the ventral striatum, the subjects also recorded differing responses in parts of the brain that indicated loneliness played a role in how their brain operates.
The researchers discussed the new field of brain mechanism in a paper in the current issue of Perspectives on Psychological Science, "What Are the Brain Mechanisms on Which Psychological Processes are Based?"
They presented the study at a symposium, "Social Emotion and the Brain," at the annual meeting of the American Association for the Advancement of Science.