The individual’s state of health is one of continual change.

He moves back and forth from health to illness and back to health again. His condition is rarely constant. He may wake up feeling great, develop a headache mid-morning, and feel fine again by noon.

The health-illness continuum (see figure 1-1) illustrates this process of change, in which the individual experiences various states of health and illness (ranging from extremely good health to death) that fluctuate throughout his life.

As we previously stated, health, just as life itself, is a process of continual change. And we must continually adapt to these changes in our lives in order to maintain good health and well-being. It is our adaptation or response to that change, rather than the change itself, that affects our health.

For example, two students just found out about a big test tomorrow, for which they are completely unprepared. One student responds to this stressful situation (stressor) by going home, getting his books out, and starting to study. The other student breaks out into a sweat, and spends most of the evening fretting over this outrage and imagining what will happen to him if he doesn’t pass the test. No doubt, this student is doing more damage to his health than is his friend. And, considering the time and energy he is expending on worrying (and not studying), he may experience even more stress when they receive their grades!

Adaptation and effective functioning, even in the presence of chronic disease, can be considered a state of wellness. A person may be in perfect physical condition, but feel too tired and “blue” to go to work, while his co-worker, a diabetic, is at work, functioning fully and accomplishing his job. Which of these two people is at a higher level on the health-illness continuum?

NOTE: Death occurs when adaptation fails completely, and there is irreversible damage to the body.