Understanding the have-knots: The role of stress in just about everything

The end result is heightened expectation of and attention to threats in the environment. Stress hormones also inhibit neuron growth in parts of the hippocampus, a brain area essential in forming new memories. In this way, stress results in memory impairments and impairs the brain’s ability to put emotional memories in context.

Think of it this way: Too much stress and you forget not to be stressed out.

These brain changes are thought by some researchers to be at the heart of the link between stress and depression — one of stress’s most devastating health consequences — as well as posttraumatic stress disorder (PTSD).

Although when we think of stressors we might think of big things like abuse, illness, divorce, grieving, or getting fired, it is now known that the little things — traffic, workplace politics, noisy neighbors, a long line at the bank — can add up and have a similar impact on our well-being and our health.

People who report more minor irritants in their lives also have more mental and physical health problems than those who encounter fewer hassles. And recent research shows that PTSD may be the result of stressors adding up like building blocks, remodeling the plastic brain in a cumulative rather than a once-and-for-all fashion.

But the best known of stress’s health impacts are on the heart.

The idea that stress directly causes coronary heart disease has been around since the 1950s; although once controversial, the direct stress-cardiac link is now well-documented by many studies. For instance, men who faced chronic stresses at work or at home ran a 30 percent higher likelihood of dying over the course of a nine-year study; in another study, individuals reporting neglect, abuse, or other stressors in childhood were over three times as likely as nonstressed individuals to develop heart disease in adulthood.

Adding insult to injury, stress may even have a selfperpetuating effect. Depression and heart disease, for example, are not only the results of stress, but also causes of (more) stress. Consequently, the chronically stressed body can appear less like a thermostat than like a wailing speaker placed too close to a microphone — a feedback loop in which the stress response goes out of control, hastening physical decline with age.

Growing evidence shows that our sensitivity to stress as adults is already “tuned,” so to speak, in infancy. Specifically, the amount of stress encountered in early life sensitizes an organism to a certain level of adversity; high levels of early life stress may result in hypersensitivity to stress later, as well as to adult depression.

A history of various stressors such as abuse and neglect in early life are a common feature of those with chronic depression in adulthood, for example.

At McGill University in Montreal, Michael J. Meaney and his colleagues have studied mother and infant rats, using rat maternal behavior as a model of early life stress and its later ramifications in humans. The key variable in the world of rat nurturance is licking and grooming. Offspring of rat mothers who naturally lick and groom their pups a lot are less easily startled as adults and show less fear of novel or threatening situations — in other words, less sensitivity to stress — than offspring of less nurturant mothers.