A new study shows that very young children who spend lots of time in centre-based childcare, or have a relatively insensitive primary caregiver, show changes in the body's stress response system that last well into adolescence.
The effects were modest, and should not alarm parents with kids in daycare, Dr Glenn I. Roisman of the University of Illinois at Urbana-Champaign, a researcher on the study, emphasised.
"This work doesn't suggest that having experienced insensitivity in the first three years of life, or having experienced centre-based care, is going to ruin a child by any means," Roisman added. Nevertheless, he added, the effects do seem to be real.
Cortisol and stress
Roisman and his team looked at a subset of 863 children taking part of the National Institute of Child Health and Development's Study of Early Child Care and Youth Development, which has followed 1 364 kids from 1 month of age through 15 years. The study includes about a dozen in-person assessments of interactions between a child and his or her primary caregiver.
The researchers looked at how parenting and childcare quality, as well as the amount of time kids spent in daycare, up until the children were 3 years old related to their cortisol levels upon awakening at age 15.
Early morning levels of this hormone are a marker for how well the hypothalamic-pituitary-adrenocortical (HPA) axis is functioning. This network of hormonal and neurological factors governs how we cope with stress long term. In a person whose HPA axis is working fine, cortisol levels are high in the morning and gradually fall throughout the day.
Low early-morning cortisol levels may signal a dysfunctional system.
Roisman and his team found a small but strong association between being exposed to insensitive caregiving (for example, parents who were detached and unemotional with the child rather than engaged and emotionally involved), and low cortisol levels. And the more time a child spent in centre-based care, the more likely he or she was to have low cortisol levels. However, childcare quality had no impact on cortisol levels.
The relationship remained after the researchers adjusted for several factors, including mom's education levels, socioeconomic status, and quality of parent-child interaction at age 15.
Early childhood experiences appear to help tune the HPA axis system so it can respond effectively to everyday stressors, Roisman noted. Studies in severely emotionally deprived children have found their cortisol levels are low when they wake up, and remain relatively flat through the course of the day.
The current study, published in the journal Child Development, included children whose experiences with parenting and childcare were in the normal range.
Useful info for parents
While the findings should not scare moms and dads who need to put their children in daycare for relatively long amounts of time, Roisman said, "I certainly think that it's a useful piece of information for parents."
"Center-based care can be stressful for young children," he added.
Other investigations have linked low cortisol levels to a greater likelihood of antisocial behaviour. Roisman and his colleagues expect to have data on how parenting and childcare influence behaviour in this group of children, who are now 17 years old, in the future. - (Anne Harding/Reuters Health, May 2009)
SOURCE: Child Development, May/June 2009.
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