Maternal Separation as a Model of Early Stress: Effects on Aspects of Emotional Behavior and Neuroendocrine Function

A growing body of findings underlines the critical role of the early environment in normal growth and development. Human studies suggest that severe stress during childhood increases vulnerability to development of affective psychopathology in adulthood. Neonatal maternal separation in rodents (rats or mice) is an established model of early stress for studying the neuroendocrine and behavioral effects of early adversity. The article reviews the existing evidence regarding the effects of this postnatal manipulation on the neuroendocrine response to stress and on emotion-relevant behaviors, and attempts to explain the existing inconsistencies seen in the results. Although the prevailing idea is that maternal separation augments emotionality and potentiates the endocrine response to stress, methodological differences among studies prevent us from making definite conclusions. Further studies in which parameters related to neuroendocrine function, behavior, and neuronal plasticity will be concurrently examined are warranted. In addition, the need to investigate whether early stress may increase vulnerability to subsequent challenges during the postnatal period is discussed.