Australian scientists said stress caused cancer cells to spread six times faster in mice. They believe stress transforms the lymphatic system into a "super highway" which then carries cancer cells rapidly around the body.
Medication used for heart problems might hold the key to preventing the spread, they said.
As a result, researchers are conducting trials of the drug Propranolol to see how successful it is at reducing stress-induced cancer spread in human patients.
Researchers at Monash University studied how stress drives breast cancer metastasis in mice, this is where cancer spreads from the original tumour to other areas of the body.
The research team placed mice with cancer in confined spaces to mimic the physiological and emotional effects of stressed humans.
They found that stress sent a signal into the cancer that allowed tumour cells to escape and spread.
"The stress is sort of acting like a fertiliser and helping the tumour cell take hold and colonise those other organs," cancer biologist Dr Erica Sloan told ABC News.
She explained that stress transformed the lymphatic system, which cancer is known to spread through, into a "super highway" - allowing it to spread at a faster speed.
Co-author Dr Caroline Le said: "You see six times more spread of cancer in stressed mice compared to control mice."
The researchers added that chronic stress can be extremely detrimental to cancer patients, particularly as it may prevent treatment from working properly.
"These findings...suggest that blocking the effects of stress to prevent cancer spread through lymphatic routes may provide a way to improve outcomes for patients with cancer," they wrote on the Monash University website.
Dr Sloan and Dr Le said medication for heart problems, which contain beta blockers, could be the key to preventing stress from increasing cancer's spread.
This is because beta blockers compete with adrenalin to limit heart rate and blood pressure increase.
Dr Sloan is now testing a drug called Propranolol on cancer patients to see if it helps tackle the problem.