I view affective and psychiatric symptoms as manifestations of the genetic expression of the chronic stress response. Accordingly from birth onward the chronic stress response is allowed expression in response to cumulatively perceived stressful events, such as emotional deprivation, frustration and rejection, traumatic experience, etc. The younger the child the greater his/her vulnerability of response to stress, as certain brain regions needed for adapting to certain stressors are simply not mature enough to modulate brain and CNS response to stress. Unfortunately this early vulnerability forms the basis for later stress reactivity and adaptability. This is later reflected in a person’s social and family history when monitored in controlled settings in human and animal neuroscience research.
“…the behavior of a mother toward her offspring can “program” (later) behavioral and neuroendocrine response to stress in adulthood. These effects are associated with sustained changes in the expression of genes in brain regions that mediate responses to stress and form the basis for stable differences between individuals in stress reactivity.” (Meaney, 2001, p. 1170).
Meaney, M.J. (2001). Maternal care, gene expression, and the transmission of individual differences in stress reactivity across generations. Annual Review in Neuroscience, 24, 1161-1192.