The Science of Early Adversity

Advances in early childhood development, especially in the science of early adversity, could revolutionize the fight against poverty

| March/April 2012

For a long time, social science has known of correlations between childhood turmoil and adult maladies that carry massive social and financial costs—mental illness, addiction, tendencies toward violence. And for decades, society has attempted to address those problems with a variety of social interventions including Head Start, which aims to prepare low-income kids between ages 3 and 5 for school; investments in school-age children; and programs for rehabilitation of juvenile delinquents.

But a scientific revolution that has taken place in the past decade suggests that many of the dysfunctions associated with childhood have roots earlier than is commonly understood—especially during the first two years of life.

Like all living creatures, human babies are hardwired with a stress reaction that kicks in whenever they perceive a threat, which can be as simple as hunger or the feeling of a wet diaper. Deep inside the adrenal glands, which sit atop the kidneys, cells pump out adrenaline—a hormone that makes the lungs breathe and the heart beat faster, increasing the supply of oxygen to the muscles.

With these hormones sloshing around, blood pressure rises, muscles tighten, energy surges, and a baby wails. When comfort comes quickly, the body produces fewer stress hormones and the brain goes back to business as usual. And if this happens repeatedly, as it should, the nerve impulses crackling in the brain will build pathways that the baby can use later in life to solve problems and overcome difficulty.

But the baby who is ignored or neglected just keeps screaming and flailing. Eventually, he exhausts himself and may appear to withdraw. Yet the quiet child is not a content child. Constant activation of the stress system causes wear and tear on the brain, so that coping and thinking mechanisms don’t develop in the same way.

Early adversity, says Charles Nelson, a neuroscientist and professor of pediatrics at Harvard Medical School, can interfere with “planning ability, cognitive flexibility, [and] memory, and all of those will correlate with diminished IQ.” Some of the children who go through these experiences end up OK—and later interventions may still be helpful for those who struggle. But, overall, says Nelson, “they’re more likely to have mental health problems.”