A person's response to the stress of physical illness varies tremendously and in large part depends on his or her own personality style and social supports. It is known, for example, that certain diseases such as diabetes, rheumatoid arthritis, peptic ulcer disease, or cardiac disease can worsen with mental stress. It is not clear or proven that stress causes diseases, but it is clear that these and probably many other illnesses are aggravated by stress. In 1967, psychiatrists Thomas Holmes and Richard Rahe found a positive correlation between a person’s life event and their illnesses. Their results are commonly known as the Holmes and Rahe Stress Scale for Adults.