The researchers found that a neurotransmitter — neuropeptide Y or NPY — released in response to stress, accelerates cell growth and cell migration.

"They will actually multiply about twice as fast and cells move around more. Both proliferation and migration are obligatory for metastasis, which is how it spreads," said lead researcher Dwayne Jackson, an assistant professor at the Schulich School of Medicine and Dentistry, who worked with PhD candidate Philip Medeiros.

The spread of cancer cells from the breast to other parts of the body makes the disease lethal.

In their research, Jackson and Medeiros looked at a branch of the nervous system known as the sympathetic nervous system. When it’s activated during stress, the sympathetic system communicates with cells through the release of neurotransmitters, including NPY.

They looked specifically at breast cancer because the female breast has a high density of sympathetic nerves.

Jackson said stress also may play a role in other cancers, but the London researchers haven’t researched the possibility.

"It is not really a leap of faith to say it likely would. We haven’t investigated," said Jackson.

Other research has shown women with a family history of breast cancer have a greater physiological response to stress.

"The actual women who have a risk for breast cancer also become stressed out under normal conditions. It kind of forms a link," Jackson said.

The research raises the possibility of new treatment strategies, such as using medications to reduce stress levels in women at risk of breast cancer.

The research was supported by the Natural Sciences and Engineering Research Council of Canada, Canadian Institutes of Health Research, and the Canadian Breast Cancer Research Foundation.