The authors accessed personal collections of reprints, scanned key journals, contacted colleagues, and searched databases such as Medline, PubMed, and OVID, between 1977 and 2003, using the keywords “cytokines and brain”, “cytokines and cancer”, “stress hormones”, “psychological stress and cancer”, “depression and cancer”, “psycho- neuroimmunology”. Only papers published in English were selected. To simplify the review, the authors arbitrarily chose the studies, in an attempt to review the
ReviewStress, depression, the immune system, and cancer
Section snippets
Physiological response to stress
Stressful experiences include physical stressors such as pathogens and toxins, and psychological stressors such as major life events, trauma, abuse, or factors related to the environment in the home, workplace, family, or neighbourhood. The ability to adjust or habituate to repeated stress is also determined by the way a person perceives a situation.6
The major neural pathways activated by stressors are the HPA axis and the sympathetic nervous system.1, 2, 3, 5, 7, 8, 9 Neurosensory signals are
Role of stress and depression
The effect of psychological factors on cancer depends very much on the type of tumour involved. Moreover, the validity of many of the data has been questioned because retrospective studies tend to show associations that are linked in the memory of individuals, and much information about real-life stressors could possibly be lost, whereas unliked phenomena are remembered less well. These observations, which are the core of psychosomatic medicine, have been rejected or ignored by many scientists
Effects on cancer
Cancer is a heterogeneous group of diseases with multiple causes, and immunological involvement varies across different cancers. Cancers induced by chemical carcinogens might be less affected by psychological, behavioural, and immunological factors than are those associated with a DNA tumour virus, retrovirus insertion near a cellular oncogene, or other viruses such as Epstein Barr virus, which is immunogenic. Suppression of cellular immunity is associated with a higher incidence of some types
Clinical implications
The determination of the role of stress in the onset and progression of cancer has faced many difficulties such as the stage of the disease and health behaviours. In addition to the direct effects of psychological states on physiological function, individuals who are stressed and depressed are more likely to have health habits that put them at great risk, including worse sleep, a greater propensity for alcohol and drug abuse, worse nutrition, and less exercise—health behaviours that have
Conclusion
Evidence mainly from animal models and human studies suggests that stress and depression result in an impairment of the immune response and might promote the initiation and progression of some types of cancer, mainly associated with a DNA tumour virus, retrovirus insertion near a cellular oncogene, and other viruses such as EBV. Through HPA activation, the mediators released during chronic stress suppress some non-specific and specific parts of the immune response, including NK-cell activity,
Search strategy and selection criteria
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