Researchers have found mounting evidence linking loneliness to physical illness and to functional and cognitive decline, according to a recent story in the New York Times. As a predictor of early death, loneliness eclipses obesity.
“The profound effects of loneliness on health and independence are a critical public health problem,” said Dr. Carla M. Perissinotto, a geriatrician at the University of California, San Francisco. “It is no longer medically or ethically acceptable to ignore older adults who feel lonely and marginalized.”
In Britain and the United States, roughly one in three people older than 65 live alone, and in the United States, half of those older than 85 live alone. Studies in both countries show the prevalence of loneliness among people older than 60 ranging from 10 percent to 46 percent.
In a paper published earlier this year in the journal Cell, neuroscientists at the Massachusetts Institute of Technology identified a region of the brain they believe generates feelings of loneliness. The region, known as the dorsal raphe nucleus, or D.R.N., is best known for its link to depression.
Kay M. Tye and her colleagues found that when mice were housed together, dopamine neurons in the D.R.N. were relatively inactive. But after the mice were isolated for a short period, the activity in those neurons surged when those mice were reunited with other mice.
“This is the first time we’ve found a cellular substrate for this experience,” said Dr. Tye, an assistant professor at the Picower Institute for Learning and Memory at M.I.T. and a senior author of the paper. “And we saw the change after 24 hours of isolation.”
John T. Cacioppo, a professor of psychology at the University of Chicago and director of the university’s Center for Cognitive and Social Neuroscience, has been studying loneliness since the 1990s. He said loneliness is an aversive signal much like thirst, hunger or pain.
“Denying you feel lonely makes no more sense than denying you feel hunger,” he said. Yet the very word “lonely” carries a negative connotation, Professor Cacioppo said, signaling social weakness, or an inability to stand on one’s own.
In his research, Professor Cacioppo has shown that loneliness affects several key bodily functions, at least in part through overstimulation of the body’s stress response. Chronic loneliness, his work has shown, is associated with increased levels of cortisol, a major stress hormone, as well as higher vascular resistance, which can raise blood pressure and decrease blood flow to vital organs. It can lead to mental health issues such as anxiety and thoughts of suicide.
Professor Cacioppo’s research has also shown that the danger signals activated in the brain by loneliness affect the production of white blood cells; this can impair the immune system’s ability to fight infections.
It is only in the past several years that loneliness has been examined through a medical, rather than psychological or sociological, lens.