Excerpt from "New Scientist" 16 December 2000 by Meredith F. Small, professor of anthropology at Cornell University. Her book, Kids: How Biology and Culture Shape the Way We Raise Our Children, published in April 2001 by Doubleday.
Human young are dependant on their carers to help them navigate through their crucial early years. So to get the emotional and physical help they need, they must be highly sensitive to the behaviour of their carers-and that makes them particularly vulnerable to family strife. Several studies have shown that it is unpredictability that really stresses kids. British researchers found, for example, that the cortisol levels of some children are lower at school, where life is predictable and stable, and higher at home, where they believe anything can happen.
Normally, their reaction to stress helps kids cope by directing energy to parts of the body that need it most, but if stressful situations are not resolved, the damage can be far-reaching. Megan Gunnar, an expert on stress in children at the Institute of Child Development at the University of Minnesota, points to a growing awareness that stress in childhood is a major mental and physical health risk.
"One reason to worry about stress in childhood is that this is the time when we learn how to manage stress-patterns that we will carry forward into our adult lives," says Gunnar. "And we don't take the hit on some of the health consequences until we are older. Increasingly, we are finding that many of those adult diseases that knock us down when we are 40 or 50- heart disease, high blood pressure and so on-are detectable in childhood, when the patterns are set."
Gunnar and others have shown that when very young children are abused, neglected or bond poorly with their carers, their cortisol levels are high even in mildly stressful situations such as play and they are unable to cope. And several recent studies of women who had been abused as children show that they are biologically vulnerable to depression and anxiety as adults because early experience permanently altered their hormonal responses, making them hypersensitive to stress.
Flinn has uncovered two abnormal patterns of cortisol production in children under continued stress from family trauma. Usually, kids have a constant low background level of cortisol, which peaks when they are under stress. But some highly stressed children have chronically high levels of cortisol. They are also shy and anxious. Another group of children has abnormally low basal cortisol levels interspersed with spikes of unnaturally high levels. They also show what Flinn calls blunted cortisol responses-their levels don't rise as they should during physical activity. Just as worrying, they are less sociable and more aggressive than kids with normal profiles.
Some of these kids have been stressed since they were conceived and they probably missed certain sensitive periods for obtaining normal cortisol profiles, though how exactly the response develops is still unknown. These children also have weakened immune responses, fall ill more frequently, are easily fatigued and don't sleep well. Looking at his record of children who are now adults, Flinn is finding that some of them seem to be permanently affected by stressful events that happened while they were in the womb, in infancy or during early childhood.