Background: The possibility that life events, personality or depression can be considered risk factors for cancer has been of great interest among the lay public and doctors.
Methods: A critical review of different publications of meta-analyses, case-control studies and cohort studies investigating a possible relation between the onset of cancer and life events, personality disorders or depression is presented. Many studies have methodological limitations with possible bias, which may explain controversial results. We selected 32 studies from which conclusions can be drawn with the least amount of bias.
Results: Eighteen out of 32 publications whose methodology permits unbiased interpretation show no link between psychological factors and the risk of cancer. Six publications show a significant link only in one or several subgroups and four surveys, three of which were published by the same author, show an inverse relation in gynecological cancers. As for life events and breast cancer, the results are slightly in favor of a positive relation in four studies; four others showed no relation and one argues in favor of an inverse risk, which means a protective effect for this cancer. For life events and other cancers, studies show no relation, with the possible exception of cancers in women where endogenous estrogens can play a role (colon and endometrial cancers), where there is an inverse relation. No studies showed a significant relation between personality features and the risk of cancer. The studies of a possible relation between depression and cancer are controversial and no conclusion can be drawn.
Conclusion: It cannot be confidently concluded that life events, personality features or depression play a role in the onset of cancer.