Loneliness raises breast cancer risk

By Sheilah Downey

People who live isolated lives, and endure the stress that creates, may be more susceptible to breast cancer, a study released today indicates.

Lab rats who lived in isolation developed elevated levels of stress hormones which resulted in a 3.3 fold increase in the risk of developing breast cancer, according to researchers at the University of Chicago.

The study is part of an on-going research program to identify the connection between breast cancer biology and social isolation. Previous studies have indicated that women living in high-crime neighborhoods deal with a variety of stressors, including isolation.

This is the first study to establish that isolation and stress can be a factor in human breast cancer risk, said study author Dr. Martha McClintock, a psychologist at the University.

"We need to use these findings to identify potential targets for intervention to reduce cancer and its psychological and social risk factors," said McClintock. "In order to do that, we need to look at the problem from a variety of perspectives, including examining the sources of stress in neighborhoods as well as the biological aspects of cancer development."

The study found that isolation led to higher production of a stress hormone, corticosterone, in rats that were kept alone and subjected to stressful situations, such as being constrained or smelling a predator.

The isolated rats experienced a 135 percent increase in the number of tumors and a more than 8,000 percent increase in the tumor's size. The impact of isolation was found to be larger than other environmental sources of tumors, including unlimited availability of high-energy foods.

Dr. Gretchen Hermes, former researcher at the University and now a resident in psychiatry at Yale University's School of Medicine, was the lead author.

The paper, titled "Social Isolation Dysregulates Endocrine and Behavioral Stress While Increasing Malignant Burden of Spontaneous Mammary Tumors," is published in the current issue of the Proceedings of the National Academy of Sciences.