Scientists have discovered that everyday emotional stress is a trigger for the growth of tumours.
They discovered that any sort of trauma, emotional or physical, can act as a "pathway" between cancerous mutations bringing them together in a potentially deadly mix.
The findings, published in Nature, seemed to show for the first time that the conditions for developing the disease can be affected by your emotional environment including every day work and family stress.
Professor Tian Xu, a geneticist at Yale University who led the study, said: "A lot of different conditions can trigger stress signaling - physical stress, emotional stress, infections, inflammation – all these things.
"Reducing stress or avoiding stress conditions is always good advice."
Until now, scientists believed more than one cancer-causing mutation needed to take place in a single cell in order for tumours to grow.
But Prof Xu and colleagues at Yale University, working with fruit flies, showed mutations can promote cancer even when they are located in different cells. This is because stress opens up "pathways" between them.
He said: "The bad news is that it is much easier for a tissue to accumulate mutations in different cells than in the same cell."