A whole field called psychosomatic medicine is concerned with psychological causes of illnesses. For a long time, ulcers were a prominent example of a psychosomatic medicine. It was assumed that high levels of stress would produce abnormal acid levels in the stomach that attacks the stomach itself. Medical research has now uncovered that it is not stress alone, but that a bacterial infection also contributes to ulcers. However, stress does aggravate the condition.
Students are more likely to be sick during exam periods than during other times of the semester.
Furthermore, people who are exposed to prolonged periods of stress, for example in wars, suffer from various somatic problems. Extreme levels of stress for prolonged periods of times can influence not only mental and social well-being, but also physical health, and may be fatal in some cases. Understanding the relation between psychological states like stress and physical health is another concern of health psychology. Health psychology is also concerned with health after an individual acquired a disease. These diseases are called chronic diseases because they are not immediately fatal.