Full context:   Disease could also be the result of the "corruption" of one or more of the humors, which could be caused by environmental circumstances, dietary changes, or many other factors. These deficits were thought to be caused by vapors inhaled or absorbed by the body. Greeks and Romans, and the later Muslim and Western European medical establishments that adopted and adapted classical medical philosophy, believed that each of these humors would wax and wane in the body, depending on diet and activity. When a patient was suffering from a surplus or imbalance of one of the four humors, then said patient's personality and/or physical health could be negatively affected.