WEDNESDAY, Dec. 9 (HealthDay News) -- Social isolation and stress may
increase breast cancer risk, new research has found.

In a study of rats by University of Chicago researchers, social
isolation and stress was associated with a 3.3-fold greater chance of
developing breast cancer. The findings also showed that rats kept alone
had a 135 percent increase in the number of tumors and a more than 8,000
percent increase in tumor size.

Being isolated and exposed to stressful situations, such as the smell
of a predator or being briefly constrained, increased production of the
stress hormone corticosterone in the animals, the study authors noted.
Isolated rats took longer to recover from a stressful situation than rats
living in small groups.

The findings, published online in the early edition of the journal
Proceedings of the National Academy of Sciences for the week of
Dec. 7 to 13, suggest that isolation and stress could play a role in human
breast cancer risk, said Martha McClintock, a professor of psychology and
comparative human development at the University of Chicago.

The researchers also have found that women living in high-crime areas
face a number of stressors, including social isolation. They noted that
black American women have been found to develop breast cancer at an
earlier age, although total incidence is similar to that of women in other
racial/ethnic groups.

"We need to use these findings to identify the potential targets for
intervention to reduce cancer and its psychological and social risk
factors," McClintock said in a university news release. "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."

More information

The U.S. National Cancer Institute has more about breast cancer risk.