On the role of immunological factors as mediators between psychosocial factors and cancer progression

Thirty-eight prospective studies on the role of psychological factors in ca ncer initiation and progression are reviewed. Despite the availability of m any prospective studies, there is no certainty about the role of any specif ic factor. An important reason might be that the interactions among several psychological factors, and the interactions of psychological and biomedica l risk factors, have rarely been studied. Some evidence has been found that a low level of social support, a tendency towards helplessness, and repres sion of negative emotions are factors that promote cancer progression. The effect of psychological factors has been more convincingly demonstrated wit h respect to cancer progression than cancer initiation, and more convincing ly in intervention than in natural history studies. Possible mechanisms med iating associations between psychological factors and disease outcome are d iscussed. The role of immunosurveillance seems modest overall, and alternat ive pathways are suggested. (C) 1999 Elsevier Science Ireland Ltd. All righ ts reserved.