Epidemiological evidence for a relationship between life events, coping style, and personality factors in the development of breast cancer
Introduction
The notion that cancer might be related to stress or emotional factors can be traced back to around 200 AD when Galen noted that melancholic women were much more susceptible to cancer than other females [1]. In 1759, Guy, a surgeon, emphasised “such disasters in life, as occasion much trouble and grief” in the causation of cancer [2]. In the first half of this century the search focused on external explanations for illness, influenced by Descartes, who viewed the mind as distinctly separate and an unrelated entity from the mechanistic body.
Renewed interest in the mind–body relationship over the past three decades parallels our increasing understanding of the complex interrelationships between the immunological, endocrine, and nervous systems. There is mounting evidence that stress can disturb many areas of the immune system and that impaired immune system function predisposes to malignant growth [3], [4]. The impact of life event stress is related not only to the type and severity of the event itself, but may be modified by the availability of resources to deal with the demands. It is unclear whether psychosocial factors impact directly on endocrine, immune, and nervous systems or indirectly by affecting behaviours such as diet, exercise, sleep, etc., which themselves have links to endocrine and immune functioning [5], [6], [7]. Hilakivi-Clarke et al. [8] have developed a model in which life event stress, personality, and social support influence an individual's ability to cope, which in turn mediates breast cancer risk via alterations in neuroendocrine and immune functioning. These data and model provide an avenue for explaining clinical and epidemiological observations in this area, as well as the anecdotal reports of women who believe that “stress” or “depression” was a factor in the development of their cancer [9], [10].
There have been many review articles published in this area, some focusing on life events, others on the cancer prone personality, some covering psychosocial factors in disease onset, and some in outcome, while others are more theoretical in nature [5], [8], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20]. However, none of these reviews have attempted to integrate the literature in these disparate areas in a systematic manner. Furthermore, many have focused on cancer in general which may cloud the picture. Because cancer is a biologically diverse disease, it is unlikely that any single psychosocial factor, or set of factors, will be related in the same fashion to the onset of all cancers.
We have chosen to focus on breast cancer, being hormonally sensitive. Since “stress” is involved in activation of the endocrine system, it seems likely that psychosocial factors may potentially play a greater role in cancer of the breast than at other sites. This review focuses on the psychosocial factors thought to be related to the development of breast cancer; namely life events, coping style, affect, personality, and social support. These areas are clearly interrelated. Although they are at times measured together, rarely are their interactive effects examined. Therefore, each domain is considered separately and where possible their interrelationships are discussed. We have chosen to focus only on predictors of breast cancer development, rather than outcome, as the literature on the latter issue is as vast, with differing predictors and theoretical pathways.
Section snippets
Method
Studies were identified from MedLine, PsychInfo, NEJM, Cinahl, and Cancerlit databases. The inclusion criteria were: an outcome diagnosis of breast cancer; assessment of one or more psychosocial risk factors; prospective, limited prospective or case–control design; at least one comparison group of healthy women, or women with benign breast disease; peer review publication in English. The exclusion criteria were: case reports; unpublished conference abstracts; conference proceedings; letters,
Methodological issues
Most studies have a limited prospective or case–control design. A limited prospective study is one in which the number of subjects required for analysis is limited by selecting those known to be at risk, such as women undergoing biopsy. These studies are usually hospital-based, with attendant sampling bias. Their strength, however, is in their capacity to evaluate psychological variables in subjects prior to confirmation of benign, malignant or no breast disease under similar conditions.
Life events
Life events are discrete occurrences of daily life, either physical and/or psychological in nature, that disrupt (or threaten to disrupt) normal life activities [35]. Events may be positive (birth of a child) or negative (illness). The impact of such events or the resulting “stress” is dependent upon the intensity of the event and an individual's resources to adapt to the event, such as coping style and social support [36].
The assessment of stressful life events is generally based on either
Coping with life events
Folkman and Lazarus [59] defined coping as “the cognitive and behavioural efforts made to master, tolerate, or reduce external and internal demands and conflicts among them.” Their Coping Strategies Inventory (or Ways of Coping Checklist), distinguishes between problem-focused coping which deals with the source of the stress and emotion-focused coping which regulates stressful emotion. We found only five studies with adequate design, directly addressing coping strategies in relation to breast
Social support
Social support is generally defined either structurally in terms of the number of individuals within one's social network, or functionally in terms of the availability of trusted individuals [64], [65]. Most research examining the relationship between social support and breast cancer focuses on the role of support after diagnosis. Only three studies have considered social support in relation to the development of breast cancer. Both Cooper et al. [24] and Edwards et al. [46] used an unspecified
Long-term emotional and personality factors
We identified 18 papers exploring the impact of long-term emotional and personality factors on the development of breast cancer, with adequate design and analysis characteristics. Most of these papers explored the impact of (a) emotional repression/emotional control/alexithymia, (b) chronic anxiety/depression, and/or (c) various related personality features (see Table 2 for definitions). Variability in study design, range of measurement tools used, and statistics reported precluded
Summary and conclusions
There is a paucity of large scale, well-designed empirical studies examining the role of psychosocial factors in the development of breast cancer. Many studies have reported on small sample sizes and convenience samples with indeterminate bias. Cases and controls from different sources were sometimes combined. Comparison groups were frequently selected from different source populations than the cases, making accurate data interpretation impossible. Response rates were at times low or not
Acknowledgements
This review was financially supported by the National Breast Cancer Centre of Australia.
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