New research is revealing that many cases of depression are caused by an allergic reaction to inflammation. Tim de Chant of NOVA writes: "Inflammation is our immune system's natural response to injuries, infections, or foreign compounds. When triggered, the body pumps various cells and proteins to the site through the blood stream, including cytokines, a class of proteins that facilitate intercellular communication. It also happens that people suffering from depression are loaded with cytokines." Inflammation is caused by obesity, high sugar diets, high quantities of trans fats, unhealthy diets in general, and other causes.