Individual Responses to Stress
Okay, so now you know that stress exerts a disruptive influence on the body and that one of its effects is an increase in the release of cortisol. It is important to note, however, that a huge difference exists between people in their ability to tolerate a given amount of stress. Some people can simply "take" a greater load of stress before they begin to break down. That said, even some of the toughest and most "stress-resistant" individuals on the planet, such as Marine Corps recruits, will still succumb to the adverse effects of stress. In one study, military recruits were subjected to five days of extreme exercise, starvation, and sleep deprivation. Not surprisingly, due to the stressful nature of this training, cortisol levels went up and performance deteriorated. The researchers also found that even after five days of rest and refueling, cortisol levels still had not returned to normal—demonstrating the fact that no matter how tough and stress-resistant you think you may be, even you have a breaking point.
In another study, this one of Swedish factory workers, differences in the stress response were compared between men and women. The researchers showed that although both male and female workers endured similar levels of stress while at work, stress levels in men fell off quickly when they left work. In contrast, stress levels among the female workers tended to either remain the same or even increase when they left work—suggesting that the women continued to be exposed to high levels of stress hormones while they looked after their family and household responsibilities (so much for gender equality).
Stress researchers frequently study competitive athletes. For obvious reasons, athletes are extremely interested in balancing the "dose" of stress they deliver to their bodies with the amount of recovery necessary for optimal performance. Counteracting the muscle-wasting and fat-gaining effects of prolonged cortisol exposure becomes a large part of maximizing performance gains while minimizing the risk for injury. For many athletes, the delicate balance between training and recovery poses a significant dilemma: To go fast, you have to train hard, but training too hard without adequate recovery will just make you slow, because you'll be tired or get hurt. Athletes who excel are those who are most adept at balancing the three primary components of their program: training, diet, and recovery. A phenomenon known as overtraining syndrome has been linked to chronic cortisol exposure—exactly the same situation that we all face in our battle with daily stressors. Although chronic overtraining is easy to recognize by its common symptoms of constant fatigue, mood fluctuations, and reduced mental and physical performance (sound familiar?), it may be difficult to detect in its earlier stages—just like the early stages of stress. Therefore, competitive athletes, like each of us, need to become adept at balancing exposure to stress with recovery from stress in order to approach the optimal physical and mental performance they (and we) are looking for.
Is There a "Weaker Sex" When It Comes to Stress?
Researchers at the Johns Hopkins School of Medicine, in Baltimore, have studied gender differences in stress response; they have found that men tend to respond to psychological stress with more "HPA axis response" while women have a greater "hormonal reaction" to stress. This suggests that men are much more likely to experience cardiovascular side effects (such as high blood pressure and heart attacks) to chronic stress, whereas women may be more likely to succumb to depression or anxiety in the face of chronic stress. That said, there are obviously a wide range of personal and individual differences between different men and different women—so it is impossible to say that all men respond to stress in one way and all women respond to stress in another way.
Scientists at Brandeis University, in Boston, have shown that the quality of one's marital relationship can either exacerbate or alleviate some of the mental stress associated with a stressful job. Those individuals with both high work stress and high levels of marital stress exhibited a flattened cortisol rhythm (suggestive of chronic stress), elevated blood pressure, and suppressed immune function. In a series of related experiments, public-health researchers in London have shown that being "overcommitted" to your work increases stress levels, elevates cortisol exposure by an average of 22 percent, and leads to a higher degree of abdominal obesity.
That's the general overview of the stress response. Acute stress followed by adequate adaptation leads to optimal long-term health. On the other hand, chronic stress followed by insufficient adaptation leads to metabolic disturbances, tissue breakdown, and chronic disease.
We all know that stress is "bad" for us—even our grandmothers knew this and their grandmothers before them. But why? The next chapter outlines some of the latest scientific theories and medical evidence suggesting that a large part of the detrimental effects of chronic stress on health may be due to the primary stress hormone: cortisol.