The Eunice Kennedy Shriver National Institute of Child Health and Human Development tracked about 1,000 children from one month through mid-adolescence to examine the effects of child care in children's first few years of life on later development.
The researchers observed children in and out of their homes and when the children were 15, they measured their levels of awakening cortisol -- a stress-responsive hormone that follows a daily cycle -- cortisol levels are usually high in the morning and decrease throughout the day.
The study, published in the the journal Child Development, said the children who, during their first three years, had mothers who were more insensitive and/or spent more time in center-based child care, whether of high or low quality, were more likely to have the atypical pattern of lower levels of cortisol just after awakening when they were 15 years of age, which could indicate higher levels of early stress.
These findings held even after taking into consideration a number of background variables -- including family income, the mothers' education, the child's gender and the child's ethnicity -- as well as observed parenting sensitivity at age 15, the study said.
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