SALT LAKE CITY, August 21, 2003 ( – Two new studies link aggressive, disobedient behaviour and increased anxiety and stress—in a minority of children—to extended time spent in daycare.

The aggression study is by the National Institute of Child Health and Human Development, and found 17% of daycare children more aggressive, disobedient and more engaged in conflict, regardless of family background, quality or type of care and temperament. The second study is from the University of Minnesota, and says shy children suffer increased levels of stress while in fulltime daycare—based on the children’s markedly higher levels of cortisol, a stress-sensitive hormone. Both studies are published in the July/August issue of the journal Child Development.

As of 2002, 64% of mothers with children under age 6 were employed outside the home, according to the U.S. Bureau of Labor Statistics—double the number in 1975. As a result, daycare is routine for a majority of children today.