The study, published in Genome Biology, provides a molecular framework for understanding why social factors are linked to an increased risk of heart disease, viral infections and cancer.
"Leukocyte -- white blood cell -- gene expression appears to be remodeled in chronically lonely individuals," Steve Cole, of the University of California at Los Angeles, said in a statement. "We found that what counts at the level of gene expression is not how many people you know, it's how many you feel really close to over time."
Researchers at UCLA and the University of Chicago used DNA micro-arrays to survey white blood cells genes from 14 individuals in the Chicago Health, Aging and Social Relations Study. Six participants scored in the top 15 percent of the UCLA Loneliness Scale, the others scored in the bottom 15 percent.
The researchers found 209 gene transcripts differentially expressed between the two groups, with 78 being over-expressed and 131 under-expressed. Those over-expressed in lonely individuals were involved in immunity and inflammation, while those under-expressed involved antiviral responses and antibody production.
Notable deaths of 2014 [PHOTOS]