May 21 (HealthDay News) -- Very young children who spent excessive time in child-care facilities or who had insensitive mothers may be more prone to stress in their teen years, a long-term study suggests.

The conclusion is based on a finding, published in the May/June issue of Child Development, that by age 15 these children are more likely to wake up in the morning with lower-than-normal levels of cortisol, a hormone related to stress. Normally, people have high cortisol levels in the morning that gradually decrease as the day continues. The abnormal pattern in these teens, the researcher said, could indicate higher levels of early stress.

The results come from the Study of Early Child Care and Youth Development in the United States, done with the Eunice Kennedy Shriver National Institute of Child Health and Human Development. For the study, researchers observed the lives of 1,000 children from infancy to mid-adolescence to try to determine how child care in early life affected their development later.

The abnormal cortisol pattern was found more often in the 15-year-olds who, during the first three years of life, spent more time in child-care centers and/or had mothers who were observed to be more insensitive. The findings held regardless of the quality of the child-care facility, the child's gender or ethnicity, the family's income level, the mother's level of education or the sensitivity the parents exhibited to the children as teenagers.

SOURCE: Society for Research in Child Development, news release, May 15, 2009