Stress as a Factor Contributing in Cancer Initiation

Although Galen had already observed a higher incidence of cancer in melancholic women, the first scientifically based preclinical and clinical studies investigating the relationship between stress and cancer incidence were not realized until the second half of the twentieth century. Preclinical studies that published Andervont (1944), Muhlbock (1951), Slawikowski (1960), Riley (1975), and others have demonstrated a higher incidence of tumors in laboratory animals exposed to stressors. However, it should be noted that not all preclinical studies have demonstrated this relationship (see, e.g., Rasmussen et al. 1963; Corson 1966). Some degree of inconsistency in this area was probably due to the fact that the experiments used different types of stressors, employed different models of tumor induction, and used different types of laboratory animals, which, in doing so, did not always meet the current standards set for health status. Therefore, the direct influence of stress on tumor-related processes has not been widely accepted and has been the subject of professional debate. However, papers published in recent years have nevertheless pointed to an important role for the mediators of the neuroendocrine stress response, namely, norepinephrine, epinephrine, and cortisol, in the processes associated with the transformation of normal cells into tumor cells (Eckerling et al. 2021). Conclusive findings have been obtained in in vitro experiments as well as experiments using animal models of cancer. Thus, for example, Silva et al. (2024) demonstrated in an in vitro study using nontumorigenic MCF-10A breast cells that activation of β-adrenergic receptors potentiated multiple processes related to breast cancer carcinogenesis. However, despite these data, the relevance of stress in human tumorigenesis still remains questionable. This is due to the fact that, in contrast to animal studies published recently, the results of clinical studies investigating the relationship between stress and tumorigenesis in humans are not always consistent. Data from some clinical studies show a relationship between psychosocial stress and the incidence of several types of cancer in humans, with the relationship being most strongly demonstrated for breast cancer and, to a lesser extent, for colorectal, lung, prostate, and pancreatic cancers (Mohan et al. 2022).