by Amy Silver

The most comprehensive child care study conducted to date to determine how variations in child care are related to children's development, supported by the National Institute of Child Health and Human Development (NICHD), found that the more hours children spend in child care, the higher the incidence of problem behavior and the greater its severity. Undertaken in 1991, the "Study of Early Child Care and Youth Development" enrolled a diverse sample of children and their families at 10 locations across the U.S. The children studied were in a range of child care arrangements including day care centers, preschools, care with nannies, and care with relatives other than their mothers.

The study was characterized by a complex and detailed study design which took into account many variables, including characteristics of the child care and the family environment. Researchers assessed children's development using multiple methods and measured many facets of children's development (social, emotional, intellectual, language development, behavioral problems and adjustment, and physical health).

Researchers followed the 1,364 children enrolled in the study in 1991 and measured their development at frequent intervals from birth through adolescence. Phase I of the study was conducted from 1991-1994, following the children from birth to age 3 years. Phase II of the study was conducted between 1995-2000 to follow the 1226 children continuing to participate from age 3 through their second year in school. Phase III of the study is currently being conducted to follow over 1100 of the children to the year 2005 through their seventh year in school.

Results indicate that the more time children spent in child care, the more likely they were to be disobedient and have trouble getting along with others. This correlation remained even when other factors such as the quality of child care, the mother's sensitivity to her child, and the family's socioeconomic status were taken into account. In fact, the time spent in child care was more strongly correlated with children's behavior than the quality of care, a finding that has provoked a storm of controversy. Greater maternal sensitivity and higher socioeconomic status correlated with better behavior in children, although they did not erase the negative effects of long hours in child care.

A second study, conducted by researchers at the University of Minnesota's Institute of Child Development, found that in children younger than age 3, levels of the stress hormone cortisol rose in the afternoon during full days in day care, but fell as the hours passed when they were cared for at home. Cortisol levels were highest and rose most steeply in children judged by day care providers to be the shyest. "These children struggle in group situations and find them stressful," according to the study's lead author, Dr. Megan Gunnar.

For more information on the NICHD study, visit www.childresearch.net.