Diurnal cortisol secretion at home and in child care: a prospective study of 2-year-old toddlers

Background: Previous studies indicate that children may experience disrupted cortisol secretion in child care. The extent to which this is a transient or long-term disruption is not known, as most studies have relied on cross-sectional designs, and age-heterogeneous small sample sizes. This study aims to (a) compare cortisol secretion measured at home and in child care at 2 and 3 years of age, (b) investigate cortisol changes from 2 to 3 years of age, (c) examine whether age at initiation of child care is associated with cortisol secretion, and (d) investigate whether cortisol secretion in child care is linked to behavioural problems. Methods: Saliva samples were collected in a cohort of children recruited at 2 years of age from a larger population sample composed of women seen for the first time during pregnancy. Saliva was sampled twice a day (morning and afternoon) over two consecutive days at home and in child care at 2 (n = 155) and 3 years of age (n = 116). Interviews regarding the familial socioeconomic background and child care history were conducted with the mothers. Results: At 2 years of age, children showed a flat diurnal cortisol pattern in child care and a decreasing pattern at home. At age 3 years, children showed decreasing patterns both at home and in child care. Also at 3 years, children with less child care experience (i.e., entry after 16 months) had higher cortisol levels in child care and lower levels at home. In contrast, those with more experience (i.e., entry prior to 8 months) had lower cortisol in child care and higher cortisol at home. Conclusion: The different patterns of diurnal secretion observed in child care as compared to home is transient for most children, diminishing as they get older, whereas home and child care overall levels later on may be influenced by the cumulated experience with child care.