In psychology, "stress" happens when we are forced to respond to a physical, emotional or environmental "stressor."
Stress can be helpful: running stresses our bones and muscles, and they get stronger. We're attacked by a saber-toothed tiger, and a quick hormonal jolt dumps sugar into our blood and redirects blood to the large muscles, in preparation for a life-or-death sprint.
But chronically elevated levels of the "stress hormone" cortisol can cause distress, and we are not talking about feeling bad. We are talking changes in the brain.
In 2007, Curt Sandman of the University of California at Irvine linked high maternal levels of cortisol at 30 to 32 weeks of pregnancy with "negative reactivity" in infants two months after birth. In English, the infants showed an unusually strong startle reaction after a sudden stimulus like a honking horn.
Cortisol measurements at other moments of pregnancy were not linked to negative reactivity (see #6 in the bibliography).
More recently, Sandman and colleagues used an MRI to show that a pregnant mother's anxiety about the course of the pregnancy affects the structure of her child's brain at ages 6 to 9.
"That maternal anxiety can change the structure of the brain in a way that appears to be permanent is quite a remarkable finding," Sandman says. The data relating brain structure to cortisol levels (rather than anxiety) have yet to be published, but will likely show the same phenomenon, he added (see #7 in the bibliography).
Curiously, generalized anxiety did not correlate with a change in brain structure. This shortage of gray matter is worrisome, Sandman says. "We know that the areas of the brain with reduced volume are related to cognition. These areas serve learning and memory, and certain of our findings with a younger cohort, at 12 months ... provide crystal-clear evidence that exposure to cortisol modulates cognitive performance."
The "modulation" is not all negative, however: High cortisol levels reduce cognitive ability early in pregnancy but later on they enhance it.
Although Sandman says the subjects in his brain-volume study were middle- or upper-class, "Our guess is that all our findings would be more dramatic in a population that had some real stresses. We have a very healthy cohort, and are still finding effects of pregnancy anxiety. We can assume that anybody who struggles with the current economic climate, and poverty, would have these stresses in much greater magnitude."
To Shonkoff of Harvard, "toxic stress" is the unifying principle in some of the mechanisms that harm young kids. The stress response is "magnificent" for dealing with acute stress, he says, but when the stress response gets stuck in gear due to the presence of a drug-addicted or physically abusive parent, a chronic stress reaction can harm the brain and other organs.
We know enough to act, Shonkoff concludes. "In the same way we understand that toxins like lead in the environment can cause organ damage, and so we screen for that, we should try to prevent or treat an overactive stress response that is producing chemicals that harm the organs."
A new focus on mitigating the chronic stresses of childhood could emerge from the American Recovery and Reinvestment Act, says Katherine Magnuson, an assistant professor of social work at the University of Wisconsin-Madison. The Act is funding early childhood advisory councils that will "look at the range of programs, at how well they are serving the need, and see what's missing. In most states, people know a lot more about early education, preschool, than about infant mental health, developmental screening for children, and making sure moms are screened for depression."
Maternal depression is prime for action, says Shonkoff. "A lot of science shows how chronic depression in mothers affects their response to their kids, and affects the kid's brain development, but no-one is connecting the dots." Verbal, physical and spoken interplay between parents and children promotes emotional and intellectual growth, he says, but depression saps energy and vitality, and therefore impairs the interaction.
Maternal depression should be a key interest of early-childhood programs, Shonkoff says. "We combed the literature and although there are lots of effective treatments for maternal depression, almost none are being evaluated for their impact on kids. If you don't have treatment focused on the interaction with the child, you get no improvement for the child, and the pattern of unresponsiveness gets hardened."
Instead, Shonkoff says, "We should combine treatment for the mother with work to help her understand how interacting with the kids is so important. It's obvious, but if you look at all the programs out there, there is no integrated approach to treatment. This is the craziness of how compartmentalized" social service programs have become, he says.
Although schools and other agencies have striven to provide enriching experiences, they are not enough, Shonkoff says. "Just providing richer opportunities is helping provide what the brain needs, but it's not helping with what the brain needs to be protected from."
Terry Devitt, editor; Steve Furay, project assistant; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive