Young children's full-day patterns of cortisol production on child care days.

OBJECTIVE To examine toddlers' full-day patterns of cortisol production on child care days and non-child care days, with a particular focus on whether the mid-afternoon elevations at child care persist into the evening or decrease to typical levels observed on non-child care days. DESIGN A prospective observational study. SETTING Four child care centers in a suburban, mid-Atlantic area. PARTICIPANTS Forty-two children aged 16 to 24 months attending full-day child care. MAIN EXPOSURE Full-day child care. OUTCOME MEASURE Salivary cortisol samples obtained at wake-up, mid-morning, mid-afternoon, and bedtime for children on 2 child care days and 2 non-child care days. RESULTS Children showed different patterns of cortisol production on child care days compared with non-child care days (chi(2)(4) = 18.21, P = .001). Child care days were characterized by an afternoon increase in cortisol levels (unlike non-child care days) and decreases to bedtime values that were comparable with levels on non-child care days. CONCLUSION Results suggest that the effects of child care on children's cortisol production are time limited across the day.