The Myth of Normal 56

of the mother’s interactions with the infant in the first days after birth on how the offspring, for the rest of their lives, respond to stress—whether appropriately and confidently or with anxiety and over-reactivity. The focus was the HPA axis, the stress-regulating feedback loop between the hypothalamus and the pituitary and adrenal glands.[*] In particular, the researchers looked at receptor molecules in the brain whose task it is to modulate stress, which is to say, to ensure the appropriate behavior when stress is present. Creatures with poorly self-regulated stress reactions will be more anxious, less capable of confronting ordinary environmental challenges, and overstressed even under normal circumstances. The study showed the quality of early maternal care to have a causal impact on the offspring’s brains’ biochemical capacity to respond to stress in a healthy way into adulthood. Key epigenetic markers—the ways certain genes expressed themselves—were different in the brains of rats who had received either more, or less, nurturing contact from their mothers.[3] Strikingly, the offspring in turn passed on to their own infants the type of mothering they had been given. Szyf and his colleagues have also shown that the quality of maternal care affects the receptor activity for estrogen—a key female hormone—in daughters, with ramifications for mothering patterns down the generations.[4] Through ingenious manipulation of the rat population studied—inconceivable in human research—both the physiological and behavioral effects of early nurturing patterns were found to be nongenetic: that is, not transmitted through the so-called genetic code, which remained unchanged. Rather, they were epigenetic—in other words, determined by how the various kinds of maternal nurturing influenced gene activity in the offspring’s brain. (The specific maternal behavior tracked by these researchers was how “lovingly” the moms “groomed,” or licked, their infants.) “Okay, but these are rodents in a lab,” you might find yourself saying. “What do these findings mean for people in the real world?” A reasonable question, to which Nature provided an eloquent answer in the form of a devastating ice storm in January 1998—in the same province, no less, where Dr. Szyf and his team did their work.[5] Considered one of Canada’s worst-