Cortisol levels of 70 children, aged 39-106 months, were sampled at home and at their full-day childcare centers at two times of day, mid-morning and mid-afternoon. Parents and teachers completed questionnaires assessing child temperament (negative affectivity, surgency or extroversion, and effortful control) and aggressive behavior. The results replicated a previous study showing increases in cortisol levels over the day at childcare for preschoolaged children, while home levels followed the expected circadian decrease in cortisol from morning to afternoon for most children regardless of age. At childcare, 3- and 4-year olds were more likely to show elevations in cortisol by mid-afternoon than were older children. Controlling statistically for age, shyness for boys, and poor self-control and aggression for both sexes were associated with increases in cortisol over the day at childcare. The results suggest that younger children and those with more immature social skills may frequently experience elevations in cortisol as the day progresses in group care contexts.
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The authors wish to thank the teachers, parents and children who helped with this research. We also would like to thank Kent Krueger and Michelle Schuder for data collecting, Pat Larson and Mary Fowler of the Endocrine Laboratory at the University of Minnesota for analyzing the saliva samples and the many undergraduates who helped with this study. This research was supported by a grant for postdoctoral studies from the National Science Foundation, Switzerland awarded to Andrea C. Dettling and the National Institutes of Child Health and Human Development grant HD16494 and Independent Scientist Award, MH56958 from the National Institute of Mental Health to Megan R. Gunnar.