Inflammation is a necessary part of the body's defences. However, inflammation which runs unchecked can lead to a host of diseases such as hay fever, atherosclerosis and rheumatoid arthritis. Inflammation has been associated with depression and a New Zealand study of 1,000 people, which followed them from birth to 32 years looked into the links between depression, childhood maltreatment and inflammation. The researchers found that those people with depression and a history of childhood maltreatment were twice as likely to have higher levels of a substance called high-sensitivity C-reactive protein which is seen as indicative of the body's level of inflammation. However people suffering from depression who had not been maltreated as children did not have elevated levels of the chemical. The elevated inflammation levels in the depressed/maltreated group were not explained by other risk factors such as low socioeconomic status, poor health or smoking.
Danese, Andrea ... [et al] - Elevated inflammation levels in depressed adults with a history of childhood maltreatment Archives of General Psychiatry April 2008, 65(4), 409-416