Psychological factors and cancer development: Evidence after 30 years of research

Abstract

The question whether psychological factors affect cancer development has intrigued both researchers and patients. This review critically summarizes the findings of studies that have tried to answer this question in the past 30 years. Earlier reviews, including meta-analyses, covered only a limited number of studies, and included studies with a questionable design (group-comparison, cross-sectional or semiprospective design). This review comprises only longitudinal, truly prospective studies (N=70). It was concluded that there is not any psychological factor for which an influence on cancer development has been convincingly demonstrated in a series of studies. Only in terms of ‘an influence that cannot be totally dismissed,’ some factors emerged as ‘most promising’: helplessness and repression seemed to contribute to an unfavorable prognosis, while denial/minimizing seemed to be associated with a favorable prognosis. Some, but even less convincing evidence, was found that having experienced loss events, a low level of social support, and chronic depression predict an unfavorable prognosis. The influences of life events (other than loss events), negative emotional states, fighting spirit, stoic acceptance/fatalism, active coping, personality factors, and locus of control are minor or absent. A methodological shortcoming is not to have investigated the interactive effect of psychological factors, demographic, and biomedical risk factors.

Introduction

After some 30 years of research, the question is still unanswered whether psychological factors have an influence on cancer initiation and progression, or not. One basis for assuming such a relationship is that several psychological factors lead to impairment of endocrine and immune function, which may in turn predispose to the development of cancer (see for a discussion, Garssen & Goodkin, 1999, Garssen & Goodkin, 2001). This question is not only of interest for scientists, but is also of importance for patients. Being diagnosed with cancer means a serious disturbance of one's personal course of life. This fate may be considered as more personal and controllable, if one's adjustment style would affect cancer progression. The interest of patients in this domain is understandable, but can also be harmful. For instance, the idea that showing fighting spirit contributes to one's cure, can lead in some patients to feeling the urge of acquiring such a coping style, even if this style does not agree with one's personality. It has been shown that cancer patients who attributed having cancer to psychological factors, such as ‘being burdened by family problems’ or ‘being emotionally repressive’, were more distressed and less hopeful than other patients (Faller, Lang, & Schilling, 1996). It would be helpful, both for researchers, for patients and for care providers who try to support patients in their adaptation process, to know what can be learned from research in this field.

Several reviews in this area have been published, 12 of which have come out since 1995 Bleiker & Ploeg, 1999, Butow et al., 2000, Cwikel et al., 1997, DeBoer et al., 1999, Denollet, 1999, Edelman & Kidman, 1997, Faller, 1997, McGee et al., 1996, McKenna et al., 1999, Petticrew et al., 2002, Petticrew et al., 1999, Sanderman & Ranchor, 1997. Some reviews did not make a distinction between truly prospective studies on the one hand, and cross-sectional or semiprospective studies on the other hand Denollet, 1999, Edelman & Kidman, 1997, McGee et al., 1996, or summarized only studies with the questionable cross-sectional/group-comparison or semiprospective design, as in recently published meta-analyses McKenna et al., 1999, Petticrew et al., 1999. Another reason is that other reviews covered only some 20–30 studies Cwikel et al., 1997, DeBoer et al., 1999, Faller, 1997. Some reviews discussed only one specific psychological factor, namely, personality Denollet, 1999, Sanderman & Ranchor, 1997 and coping (Petticrew et al., 2002), and four other reviews were restricted to the role of psychological factors in the initiation of breast cancer Bleiker & Ploeg, 1999, Butow et al., 2000, McGee et al., 1996, Petticrew et al., 1999.

This overview summarizes 70 longitudinal prospective studies, concerning the domains of stressful life events, social relationships, distress level or number of psychological problems, having a psychiatric diagnosis, repression, coping style, and personality factors in general, and loss events and locus of control in particular. These domains, depicted in Fig. 1, concern potential psychological risk factors for cancer development and are most often studied and discussed in reviews.