Doctors have long suspected that social networks have direct biological effects on health. Now researchers have found a way to test the idea, and it's turning out to be true. Some very creative research at the University of Chicago has found a way to connect the isolation and fear experienced by women living in a high crime neighborhood of Chicago to the accelerated growth of "triple negative tumors," a particularly frightening type of breast tumor that's most prevalent in women of African descent.
With a very smart and deliberate series of experiments, researchers found that a surge in the stress hormone cortisol caused by social isolation works through receptors on the surface of tumour cells to increase the activity of certain genes. This loneliness-induced shift in activity allows tumor cells to use sugar and fats more efficiently to grow. But this connection between increased tumor growth and an uptick in the stress hormone cortisole associated with social isolation is not the only intriguing finding.
Women in one phase of the study who had developed triple negative tumors also had a disproportionately high incidence of a condition known colloquially as cortisol burnout; their cortisol levels did not rise and fall in response to stress as cortisol does under normal conditions. Instead, about two-thirds of the the women with breast cancer were what researchers call "flatliners," with constantly low cortisol levels. This type of condition has been studied in people with post-traumatic stress disorder and is thought to be a result of overproduction of cortisol that eventually erodes the body's ability to release the stress hormone. Women who felt they had a strong social network and scored low on a psychometric test for loneliness were insulated from the stress, and were more likely to have a normal cortisol cycle.