The term stress has appeared since the 17th century and its meaning and its uses have constantly evolved, currently being used both in common and scientific language (more in the social and medical field, but also in construction and in the field of materials study) . The introduction of the term into the medical literature is generally attributed to Hans Selye who was an endocrinologist (he used it in 1946), although the term was already used in the psychiatric literature to describe mental tension. Some of Selye’s experiments and published works took place between 1936-1956, a period in which the current of behaviorism in the field of psychology also emphasized animal experiments and in medicine the idea that stress could play a role in the emergence of diseases was circulating. In addition, due to World War II and the Korean and Vietnam wars, interest in stress also increased in the military field, being concerned with individual vulnerabilities and the effects of stress on military performance. Gradually the emphasis was also placed on the differences in the way danger is perceived and after the 1960s the way people deal with technological progress, the effects of flying outside the Earth, the effects of noise on productivity (later speaking of occupational stress) was also studied ). In line with these researches, Richard Lazarus believed that the differences identified in the perception of stressful elements depend on how each person cognitively evaluates them. In this way, Lazarus emphasizes the role of mental processes and creates a coherent theoretical framework for introducing mental processes as intermediate elements in the occurrence of stress. Later, research included the relationships between the psychic, nervous and immune systems leading to the development of psychoneuroimmunology (PNI). The results obtained in this field lead to the conclusion that the cognitive evaluation of stressors is very important and that stressors (regardless of whether they are few and strong or, weaker but many) can lead to a decrease in the immune response, thus favoring the appearance of diseases.