A study of bereaved parents shows that stress, in itself, does not cause cancer.

It's widely believed that there must be a link between undue stress and heighened risk of cancer. On theory is that stress undermines the immune system, so it is less vigilant to the development of cancer cells. Another idea is that stress increases the likelihood of risky behaviours, like smoking - but is not itself causal.

Researchers in Denmark looked at data on over 21,000 parents who had lost a child - generally agreed on as a very stressful event. They compared them with over 200,000 parents who did not lose a child. Overall, there was no higher risk of cancer in parents who had lost a child. However, there was a slight increase in risk in smoking-related cancers - and lung cancer in particular - among women who had lost a child. This suggests that maybe stress causes an increase in smoking which, in turn, raises the risk of lung cancer.

Source

Cancer 15th November 2002 (on-line edition from 31st October)