Does psychological stress and other social stresses in humans affect cancer risk? This was a big question that was hovering for many decades among people and scientists contemplating the causes of cancer. There is a widespread public belief that psychological stress leads to disease, including cancer. Medical studies and clinical evidence were observing that stressful events in humans can alter the levels of hormones in the body and adversely affect the immune system. But there were many difficulties to support clear evidence that these changes could lead to mechanisms of
initiation and progression of cancer and increased risk to develop neoplastic tumours. Studies in the 1980 and 1990s suggested that psychological stress and stress variables (death of children, relatives, divorce, separation,health worries, etc.) can cause cancer, particularly breast cancer. But the evidence for this has not been substantiated by recent studies with high numbers of participants. Women diagnosed with breast cancer frequently attribute their cancer to previous periods of psychological stress, and adverse life events prior to diagnosis, but scientific evidence is inconclusive. While some studies have found a link between breast cancer and psychological stress, they have often only looked at a small number of participants or asked women to recall if they were stressed before they developed the disease. Scientists observed that psychosocial stress in humans
leading to physiological stress response, increased secretion of hypothalamic and pituitary stress hormones. These stress biomarkers can trigger and maintain chronic inflammation, which has been shown to have various roles in cancer initiation and progression. Another dimension of stressful life events is increased unhealthy habits, like tobacco smoke, alcohol consumption, excessive food intake, obesity and lack of exercise. All these changes in life style are associated risk factors for chronic inflammation, carcinogenic mechanisms and increased cancer risk. Also, healthcare professionals hold the view that stress has a role in the development of the disease, but these views might be from recall bias (patients possibly over-reporting past exposures to stress). But in the most recent epidemiological study with the participation of high numbers of cancer patients, the results have found that stress does not increase the risk of cancer. Researchers combining the results from many different studies (meta-analyses, including over 100,000 people, 2013) found no link between stress and bowel, lung, breast or prostate cancers. This review is a systematic compilation of research papers, scientific reports, epidemiological and meta-analysis studies on the possible association of psychological stress with chronic diseases, inflammation and cancer.
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