Researchers say a number of drugs currently used to treat autoimmune diseases also appear to treat signs of depression. These medicines are known as anti-inflammatories. They help to reduce inflammation in the body. Inflammation is the pain and expansion, or swelling, of damaged tissue. An autoimmune disease is a disease where the body attacks itself. Examples include the skin condition psoriasis, rheumatoid arthritis, type 1 diabetes and Crohn's disease. White blood cells are part of the body’s natural defense against disease. They help to protect us against infection. In autoimmune diseases, the white blood cells are over-activated. Instead of simply attacking bacteria and viruses, the body’s natural defense system also attacks healthy tissue. To treat an autoimmune disease, patients often are told to take anti-inflammatory drugs. Now, a study suggests that the drugs also appear to treat signs of depression.