The literature is replete with examples of the impact of stress on physiologic systems and behavior. For example, our group finds that exposure to a prolonged, unpredictable and non-habituating stress regimen (which we call “chronic variable stress,” or CVS) causes marked increases in cumulative glucocorticoid secretion, sensitization of hypothalamo-pituitary-adrenocortical (HPA) responses to new stressors, decreased heart rate variability, reduced weight gain, decreased sucrose preference and increased immobility in the forced swim test (Herman et al., 1995; Ulrich-Lai et al., 2006, 2007; Jankord et al., 2011; Flak et al., 2012), suggesting functional changes across a variety of neurobehavioral systems in the brain. Whereas it can be argued that the net result of these physical and behavioral changes would be maladaptive, one has to interpret them with respect to the new context of the individual. Most responses to chronic stress are adaptive, that is, beneficial to the survival of the animal. For example, increases in corticosteroid levels promote mobilization of energy, important in times of need. Corticosteroids also inhibit systems that channel resources to functions such as growth and reproduction, not necessarily
