Rearing experiences and stress-induced plasma cortisol as early risk factors for excessive alcohol consumption in nonhuman primates

Background: The purpose of this study was to assess the impact of early rea ring and stress-induced rise of plasma cortisol collected during infancy as a biological predictors of adult alcohol consumption in nonhuman primates. Methods: Ninety-seven female and male rhesus macaques (Macaca mulatta) were investigated. They were reared for their first 6 months of life either wit hout mothers or other adults but with constant access to same-aged peers (p eer-reared), or as controls with their mothers (mother-reared). When subjec ts reached 6 months of age, they underwent a series of four sequential week s of 4-day social separations. Blood was drawn 1 and 2 hr after initiation of the 4-day separation periods, and the plasma was assayed for plasma cort isol concentrations. When the subjects were young adults (approximately 50 months of age), they were tested for voluntary intake of alcohol for 1 hr p er day, 4 days a week, during a period of 5 to 7 weeks under normal living conditions. Results: The social separation challenge increased infant plasma cortisol c oncentrations, with peer-reared subjects exhibiting higher stress-induced c ortisol concentrations than mother-reared animals. Subjects that responded to the social separation challenge with high cortisol levels consumed signi ficantly more alcohol per kilogram of body weight as adults than subjects w ith a low cortisol response to the separation challenge, regardless of rear ing condition. In addition, male and peer-reared subjects consumed signific antly more alcohol than female and mother-reared subjects, respectively. Conclusions: These findings suggest that early rearing experiences, such as adult absence, and high plasma cortisol concentrations early in life after a social separation stressor, are useful psychobiological predictors of fu ture high alcohol consumption among nonhuman primates.