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.