Peer pressures: Social instability stress in adolescence and social deficits in adulthood in a rodent model

• There are behavioural and physical parallels between adolescence in rats and humans.
• Adolescent social instability stress in rats impairs adult social behaviour.
• The developmental trajectory of the hippocampus is altered by adolescent stressors.
• Age differences in stress-induced corticosterone release are stressor-specific.
• Animal models provide insights into developmental stage-specific vulnerability.

Studies in animal models generate and test hypotheses regarding developmental stage-specific vulnerability that might inform research questions about human development. In both rats and humans, peer relationships are qualitatively different in adolescence than at other stages of development, and social experiences in adolescence are considered important determinants of adult social function. This review describes our adolescent rat social instability stress model and the long-lasting effects social instability has on social behaviour in adulthood as well as the possible neural underpinnings. Effects of other adolescent social stress experiences in rats on social behaviours in adulthood also are reviewed. We discuss the role of hypothalamic–pituitary–adrenal (HPA) function and glucocorticoid release in conferring differential susceptibility to social experiences in adolescents compared to adults. We propose that although differential perception of social experiences rather than immature HPA function may underlie the heightened vulnerability of adolescents to social instability, the changes in the trajectory of brain development and resultant social deficits likely are mediated by the heightened glucocorticoid release in response to repeated social stressors in adolescence compared to in adulthood.