Psychoanalytic theories have long posited that repressed emotions can manifest themselves as physical symptoms. Franz Alexander, a psychoanalytic theorist, found that a repressed need to cry can lead to lung spasms and asthma and repressed anger can lead to a temporary increase in blood pressure. Though these experiments were not generally accepted because they incorrectly assumed the long-term stability of these emotions, they were somewhat confirmed by later research conducted by Sinha et al. (1992) which observed an increased heart rate with emotions such as anger, fear and sadness. So the question remains, can short-term stress really play a role in developing sustained physical illness? 
Though psychologists and psychiatrists first introduced this question, it was later developed by a physiologist Hans Selye (1907-1982). Selye conducted research on mice whereby he simulated a stressful situation through forced immobilization; pinning the mice’s paws to the ground. This stressful incident allowed the mice to develop perforated peptic ulcers. His influential work launched the concept that stress could, in fact, be a determinant of illness. 
Using ulcers as an example of physical illness, epidemiological research also confirmed the link between acute stress and physical illness. In her paper, “The Very Model of a Modern Etiology: A Biopsychosocial Review of a Peptic Ulcer,” Levenstein (2000) confirms the link between job frustration, dissatisfaction about wages, family problems, and low socioeconomic status and the development of ulcers. Some of the epidemiological evidence even goes back to World War II, with the observation that hospitalizations for peptic ulcers among residents of London increased significantly following the German bombardment. 
Despite these findings, the concept of stress instigating the development of peptic ulcers is still puzzling given that stress actually reduces gastrointestinal (GI) activity. A model proposed by Levenstein (2000), suggests that the release of cortisol, also known as the “stress hormone”, following an acute stressful event, can actually lower one’s immune response making them more susceptible to ulceration by reduced protection against H. pylori, a bacteria found in the GI tract. Through this mechanism, acute stress can contribute to the progression of cancer, the common cold, and HIV/AIDS. However, long-term stress can also bring about physical disorders such as cardiovascular disease and rheumatoid arthritis, through a paradoxical mechanism: a heightened immune response. Psychoneuroimmunological research reveals that long-term stress can desensitize one’s cortisol receptors, leading to an increased immune response. 
Several scholars have confirmed the link between stress and physical illness, and have even provided plausible mechanisms. But, if everyone experiences life stressors on a daily basis, why are not we all constantly sick, ulcerated and hypertensive? It seems that our susceptibility to developing a physical illness is highly dependent on our appraisal of different life stressors. 
Psychologist Richard Lazarus first proposed the appraisal theory of stress. The first stage is primary appraisal, during which you develop an interpretation of the stressor. It may be perceived as negative or positive and challenging or threatening. For example, let’s consider a man who has just lost his job. If he is at retirement age, he may interpret the situation in a positive manner, realizing that it could be an opportunity to try new things. However, if this man was at a financially trying time in his life, that same event could be interpreted as negative and a threat. This idea is supported by Levenson’s (1979) study. He showed that when asthmatic kids watched a movie clip about asthma, they experienced more respiratory resistance, than when those same kids watched a clip depicting an industrial accident or adoption (topics less relevant to their condition). This revealed that their appraisal of the clip as relevant and stressful catalyzed a harmful physical response. The second step in the appraisal process is secondary appraisal, whereby one determines if he or she possesses the tools necessary to cope with a given situation. Those who have a low sense of self-efficacy are more likely to develop a physiological response.