Stress and cancer

Stress is a term that has been variously defined in the literature. In the context of research into psychophysiological aspects of cancer, 'stress' usually refers to stressful events occurring in people's lives, such as bereavement or unemployment. The effects of stress in terms of psychological morbidity and physical illness are being studied more and more. Experimental work has been conducted using animals but the results are contradictory and inconclusive. It is postulated that the effects of stress are mediated hormonally or immunologically, and there is evidence in support of this view from both animal experiments and human studies. Other mechanisms may also exist. Observations that stress is implicated in the onset of cancer have been traced back to the sixteenth and seventeenth centuries. Early studies were methodologically flawed, however, and results from recent, more carefully controlled investigations have not supported consistently the connection between stress and cancer. The methodological problems to be overcome in this area are still enormous, not least that of causality: because the data of onset of malignancy is uncertain, it is impossible to know whether a stressful event preceded or followed the genesis of cancer. Recurrence of cancer is easier to date and more amenable to study. The contributory role of stress in recurrence or reactivation of tumour growth may be a more fruitful line of inquiry. Different methods for measuring stress are available. Questionnaires which patients complete themselves have been criticized on the grounds that they ignore the meaning and context of stressful events, and because their scoring systems imply additivity. Interview methods are superior and reliable, although more costly and time consuming. Studies that seek to measure the effects of stress on the course of cancer should control for intervening variables such as personality and social support.