Final answer:
Research has shown that chronic stress can have detrimental effects on the immune system, making individuals more susceptible to illnesses, including the common cold. Although an exact percentage of illnesses caused by stress is uncertain and varies, it is recognized as a significant factor in health.
Step-by-step explanation:
Stress has a significant impact on health, often contributing to a variety of illnesses. Research, such as the studies by Cohen et al. (1998), has shown that people experiencing chronic stress are more likely to contract illnesses such as the common cold. This is due to the negative effects of stress on the immune system, which lowers its ability to ward off infections.
Concerning the percentage of illnesses that can be attributed to stress, it is difficult to pinpoint an exact figure, as it varies widely depending on the specific illness and individual circumstances. However, it is clear that stress can contribute significantly to especially when stress is chronic and not managed effectively.
It is important to understand that not all stress has negative effects on health—brief and acute stress may even boost the immune system. However, when stress is prolonged, it can lead to a weakened immune response, leaving the body more susceptible to various illnesses.
Therefore answer is Option 2: 30-50%.