A. In response to acute stressors (forced swim), neonatally injured adults take significantly longer to initiate floating. By contrast, adults injured early in life float rapidly after exposure to 7 days of mild chronic variable stress (mCVS). B. Hypo-sensitivity to acute stress-provoking stimuli and hyper-sensitivity to sequential, unpredictable stress are rescued if male and female rats are given morphine for early life pain, suggesting that 1) injury-induced behavioral and hormonal vulnerability are preventable, 2) neonatal pain is necessary for the long-term changes in stress responding. (Abbreviations: corticosterone, CORT; area under the curve, AUC).