Examining infants’ cortisol responses to laboratory tasks among children varying in attachment disorganization: stress reactivity or return to baseline?

Bernard, Kristin
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University of Delaware
Cortisol is a hormone involved in mounting a stress response in humans. During infancy, however, cortisol appears to be relatively unresponsive to a number of stressors. This developmental period of cortisol hypo-reactivity in human infants may be similar to the stress hyporesponsive period (SHRP) in rodent pups. In both rodent and human models, maternal care has been implicated as an important factor in the regulation of infants’ physiological responses to stressors. However, findings regarding this effect in humans have been relatively ambiguous due to lack of adequate baseline measures of cortisol activity. In the present study, the order of two laboratory tasks (i.e., Strange Situation and play) was counterbalanced and home saliva samples were obtained in order to control for basal activity of cortisol more systematically. Saliva samples were also collected upon arrival at lab, and at 40, 65, and 80 minutes after arrival. Changes in cortisol were examined using piecewise hierarchical linear modeling, testing whether observed increases reflected a return to baseline or stress reactivity. An interaction between attachment disorganization and task emerged, such that disorganized infants showed increases in cortisol in response to the stressor compared to play, whereas organized infants did not show cortisol reactivity to either task. Implications for the buffering effects of maternal care on the maintenance of hyporesponsivity in infants are discussed.