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 (χ₄ ²=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.