"Loneliness has been linked to everything from heart disease to Alzheimer's disease. Depression is common among the lonely. Cancers tear through their bodies more rapidly, and viruses hit them harder and more frequently. In the short term, it feels like the loneliness will kill you. A study suggests that's because the pain of loneliness activates the immune pattern of a primordial response commonly known as fight or flight."

"For decades, researchers have been seeing signs that the immune systems of lonely people are working differently. Lonely people's white blood cells seem to be more active in a way that increases inflammation, a natural immune response to wounding and bacterial infection. On top of that, they seem to have lower levels of antiviral compounds known as interferons."

"That seemed to provide a link to a lot of the poor health outcomes associated with loneliness, since chronic inflammation has been linked to everything from cancer to depression. The human body isn't built to hold a high level of inflammation for years. "That explains very clearly why lonely people fall at increased risk for cancer, neurodegenerative disease and viral infections as well," saysSteve Cole, a genomics researcher at the University of California, Los Angeles, and lead author on the study published in the Proceedings of the National Academy of Sciences on Monda."