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352 REVERSIBLE DISORDERS OF BRAIN DEVELOPMENTsocial/pair bonding (reviewed by Young & Wang, 2004). These neuroendocrinedeficits persisted even after the children were placed in nurturing families.Preclinical and clinical evidence clearly demonstrates that young organisms exposedto maltreatment or other forms of extreme stress are likely to have elevatedneurobiological risk factors, and in humans this can indicate an increased likelihoodof developing psychiatric illnesses such as depression and PTSD. Currently it is notwell understood which neurobiological changes are reversible or permanent, norwhether there are particular windows of opportunity for intervention.Stress InoculationIn contrast, recent research has indicated that exposure to mild to moderate stressors(particularly challenges that the young organism can successfully manage ormaster) can provide inoculation to subsequent stressors, creating a hardier or moreresilient phenotype. Lyons et al. exposed young squirrel monkeys (postnatal 17–27 weeks) to mild early life stressors (short-term isolation by removal from contactwith other monkeys). Upon subsequent evaluation of the monkeys’ ability tocope with new challenges, the team found that the stress-inoculated monkeys hadreduced production of potentially damaging stress hormones such as adrenocorticotropichormone (ACTH) and cortisol. In addition, the group that was exposedto mild stress demonstrated better socioemotional functioning than the nonstressedgroup, evinced by fewer anxious behaviors, bolder exploration of the environs,and larger food consumption (Parker et al., 2004). Subsequent work by Lyons andcolleagues indicated that young primates who were exposed to mild to moderatestressors demonstrated improved functioning of the prefrontal cortex (PFC), whichmay in turn enhance cognitive performance in areas that are reliant on the prefrontalcortex (Parker et al., 2005).Research on U.S. Special Forces soldiers by Morgan, Southwick, and Charney(Morgan et al., 2000) has similar implications for stress inoculation. Special Forces(SF) troops are thought to be more “stress hardy” than most other soldiers, due inpart to the rigorous stress inoculation training they receive in U.S. Army survivalschool and at the various challenging levels of military training that they mustcomplete before entering the Special Forces training program. This study lookedat levels of neuropeptide Y (NPY) concentration in SF and non-Special Forcessoldiers under the stressful conditions of survival school. NPY is a 36-amino acidpeptide that is released with norepinephrine when the sympathetic nervous system(SNS) is strongly activated. NPY regulates CRH-related activity at theamygdala, reduces locus coereulus firing, and inhibits the continued release ofnorepinephrine so that the SNS does not “overshoot.” NPY is also thought to conferneuroprotection and anxiolysis (Heilig et al., 1994; Heilig & Widerlov, 1990). Ithas also been negatively associated with dissociation during a stressor (Morganet al., 2000), and is found in lower concentration in combat-traumatized veteranswith PTSD as compared to healthy controls (Rasmusson et al., 2000). The results