Cortisol levels of young children in full-day childcare centers: relations with age and temperament.

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 preschool-aged 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.