Researchers found stressed cells can generate tumour-inducing signals that affect their neighbours.

Although the study was carried out on fruit flies, the same genes and biological pathways involved are found in humans.

Chronic inflammation, a key cause of stress, is already known to be associated with tumour growth in human cancer patients.

Some experts believe negative emotions, stress hormones, inflammation and cancer may all be linked, but the evidence is not clear.

The research is reported in the journal Nature.