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Med Sci Monit 2005; 11(5): RA147-154
Clinical and pre-clinical evidences prove that among many individuals experiencing stress, only a sub-population will progress to disease. Thus, understanding the causes of individual differences and the consequences of variation in vulnerability is of major importance. The aim of this review is to shed light on this issue by discussing results obtained on a new naturalistic model of chronic psychosocial stress in male mice. Resident/intruder pairs of mice lived in continuous sensory contact and physically interacted daily. Four categories were identified: resident dominant, resident subordinate, intruder dominant, and intruder subordinate. Of these groups, I will discuss here the results obtained in the resident subordinate group. A resident subordinate mouse owned a resource, i.e. a territory, before an intruder mouse won the social competition and became the dominant in that territory. Resident subordinates showed a unique profile of immuno-endocrine alterations and metabolic disorders, suggesting that the loss of relevant resources, such as territory, can be one key factor determining why only certain stress-exposed individuals ultimately show malignancy and psychopathologies. An analysis of the human and animal literature suggests this conclusion to be true for a variety of pathologies linked to chronic stress exposure.