5.2: Stress and Disease

The relationship between stress and health is complex. Each person perceives and responds to stress differently and there are different types of stresses, both good and bad. For some people, it happens before having to speak in public. For other people, it might be before a first date. What causes stress for you may not be stressful for someone else. With so much variation in stress, it is challenging to determine the exact relationship of stress and disease. However, since about the 1940’s scientists and researchers have been working to better understand the relationship.

People experience both eustress and distress. A person experiences eustress, also referred to as “good stress,” when the stressor helps the body enhance performance or overcome lethargy, it is their optimal level of stress. Distress, or what we view as “bad stress,” is when the body cannot cope with the stressor and leads to fatigue, or behavioral and physical problems. Stress can be helpful if it encourages you to meet a deadline or get things done. But feeling stressed for an extended amount of time can take a toll on your mental and physical health.

Optimal Stress

Although we tend to associate stress and health negatively, there is also a positive association between stress and health. Some stress can be good for you and help you to reach optimal performance. The relationship between stress and optimal performance is called the Yerkes–Dodson law, developed in 1908. Although this is called a law, it is actually a concept explaining that we need a certain amount of stress (arousal) to reach optimal (strong) performance. If we have too little stress or too much stress our performance will weaken. If we are under-aroused, we become bored and will seek out some sort of stimulation. On the other hand, if we are over-aroused, we will engage in behaviors to reduce our arousal/stress.

Figure \(\PageIndex{1}\): Yerkes-Dodson Theory of Optimal Arousal

Most students have experienced this need to maintain optimal levels of arousal (stress) over the course of their academic career. Think about how much stress students experience toward the end of spring semester—they feel overwhelmed with work and yearn for the rest and relaxation of summer break. Their arousal/stress level may be too high. Once they finish the semester, however, it doesn’t take too long before they begin to feel bored; their arousal level is too low and their level of performance or productivity is also typically lower. Generally, by the time fall semester starts, many students are ready to return to school. This is an example of how the arousal theory works.

General Adaptation Syndrome

In the 1930’s a young medical student named Hans Selye became very interested in the relationship of stress and disease and for the next 50 years he systematically studied its relationship. One of his biggest contributions to the field of study was his development of the General Adaptation Syndrome. Selye found that there seemed to be a common or typical stress response pathway that people experienced when confronted with a stressor.

The pathway is simplified into three stages: Stage 1- Alarm, Stage 2- Resistance, and Stage 3- Exhaustion. This pathway begins when a person is exposed to a stressor and they are at first taken off guard and the body launches the Fight or Flight response (alarm stage). If the perceived stress continues, they attempt to maintain homeostasis by resisting the change (resistance stage). Our body wants to stay in homeostasis, which is a state of physiological calmness or balance, and occurs when our bodily functions are running smoothly in conjunction with low stress levels. Finally they eventually fall victim to exhaustion due to prolonged exposure to the stressor and depleting the bodies ability to cope to maintain homeostasis (exhaustion stage). Reaching the exhaustion stage leads to illness due to the resulting wear and tear on the body which leads to suppressing the immune system and causing bodily functions to deteriorate. This can lead to a variety of health issues and illnesses, including heart disease, digestive problems, depression, and diabetes.

For example, you just find out that you have to pass a certification test in 2 months in order to keep your job and have not started studying. Your first reaction might be shock, anger, feelings of hopelessness, or anxiousness. This is the first stage, the alarm stage. You could choose to quit your job and flee from the stress, however you know how important it is, so you make a plan to prepare the test and include deep breathing exercises. In this stage you are resisting the stress with coping mechanisms. As the certification test gets closer you once again begin feeling stress, you might feel like you are doomed to fail this test and feel desperate, feel constantly anxious, have difficulty falling asleep and waking up in the morning. This is the exhaustion stage and where you will be more susceptible to getting sick. The exhaustion of this stage will have deleterious effects on your health by depleting your body resources which are crucial for the maintenance of normal functions. Your immune system will be exhausted and function will be impaired.

Psychoneuroimmunology (PNI)

Unlike the Yerkes-Dodson Law or the General Adaptation Syndrome, Psychoneuroimmunology (PNI) is not a model or framework, but rather a discipline of study. People who study the discipline of PNI study the relationship between the endocrine system, the nervous system, and the immune system to better understand the connection between the mind and the body.

For example, in the 19080’s a married couple, one a psychologist and the other an immunologist, began to become aware of the growing body of research in PNI and realized they had a unique opportunity to bring their disciplines and perspectives together to add to the research on the relationship of stress and disease^[1]. Rather than continue with research using animals, as many had before them, they wanted to study the connection between stress and immunity under more natural circumstances. This began years of researching medical students before, during, and after taking a very stressful 3-day exam. They found that the stressful exam brought about a decline in the students’ Natural Killer cells, one of the main immune cells that fight off disease.

There is a wealth of research on how stress impacts immune functioning leading to the belief that every one of the hormones/transmitters secreted by these nervous system regions has been shown to have the potential, either in vivo or in vitro, to alter some aspect of immunity^[2]. It has been found that chronic stress is an immunosuppresive, meaning that it suppresses the immune system not allowing the body to have an efficient and effective immune response. It is now well established that psychological factors, especially chronic stress, can lead to impairments in immune system functioning in both the young and older adults.