Early life stress: long-term physiological impact in rodents and primates.

Rat, monkey, and human infants have evolved to expect certain patterns of care. Spontaneous or experimental deviations of care from the norm result in infant stress responses. Hyperactivity of immature stress systems such as the limbic-hypothalamic-pituitary-adrenal axis and the limbic-sympatho-adrenomedullary axis can alter their subsequent reactivity across the life span.