Stress is potentially a very healthy state of mind under which much good work and happiness is found. Stress is also potentially fatal.

Distress

When we talk of bad stress (DIStress), we're talking about something that is directly causing the brain and body to shrink in its working capacity, resulting in low-performance levels. It is caused when a person is feeling anxious, threatened (maybe embarrassed, pressed for time, loss of prestige) or overwhelmed with feelings of helplessness. This occurs when a person feels he or she:

1. Is being forced to face a challenge that he does not want to ("I do not want to do it");
2. Cannot think of a solution to the challenge ("I do not know how");
3. Lacks the resources (internal, as in brain capacity, or external as in materialistic) to solve the challenge ("I cannot do it");
4. Has little or no control over the situation ("I am helpless").

These perceptions can be real (the person actually has no control or power over changing the situation) or imagined (the person could have influence over the situation) but the effects are the same: the person feels threatened and in danger. This danger could be physical safety or to his psychological state of mind.

Biological response to distress

Sometimes you feel so stressed that you'll tear your hair out!

Physiologically, there are a few things going on inside the body to promote these feelings of distress: One of the hormones released is cortisol. This can cause the hippocampus, an important part of the brain, to react in a negative way. The hippocampus is responsible for local memory, indexing systems (where the brain stores information) and is also involved with the immune system. The release of cortisol can weaken the effective functioning of the hippocampus, which makes some of the body's systems (e.g. immune system) to slow or shut down. In response, the person experiences a decline in learning ability, motivation, emotional resiliency, strength and capacity to remain healthy.

This is the traditional way of understanding why and how stress affects the body. For a more current view on what goes on in the body on a molecular level, go to the biochemistry of emotions.