Psychosocial factors and psychophysiological mechanisms in the aetiology and development of cancers.

Socio-cultural factors which may play a contributory role in the aetiology of cancer have been extensively investigated and it is well established that the incidence rates of different forms and sites of the disease are not equally distributed throughout the population. Social class, occupational, environmental and 'life-style' differences, amongst others, have been found to be associated with an excess risk of cancer, although the argument concerning the relative importance of these various factors remains a controversial one. It seems increasingly clear however, that there are large behavioural components which govern exposure to potential carcinogens and there is growing interest in the extent to which social and psychological demands may be associated with these agents or may operate as contributory factors in their own right. A number of early studies of psychological approaches to the study of cancer aetiology are reviewed from a methodological perspective. Much of the early work suffered from the problem that psychological characteristics of individuals who already had cancer were used to construct models concerned with aetiological factors. A number of the more recent studies which have attempted to overcome these difficulties are discussed. Tentatively, these later investigations suggest that two main groups of factors are related to an increased risk of cancer. First, the loss of, or lack of closeness or attachment to an important relation (often a parent) early in life, and second, the inability to express hostile feelings or more generally the abnormal release of emotion. Several psychophysiological mechanisms are reviewed which have attempted to account for the relationship between psychological disturbances and the onset of cancer, particularly the growing evidence which implicated a role for the immune system as a link between the central nervous system and disease processes.