As things stand most people who are treated for depression are partially responsive or non-responsive to conventional antidepressant medication. Rates of depression continue to increase and, according to the Depression and Bipolar Support alliance, the U.S. economy spends around $70 billion annually on lost productivity, medical expenses and assorted expenses. The cost to the individual and their relationships is incalculable. Increasingly the calls for a switch in direction have been getting louder and one of these involves more focus on inflammation as a cause of depression.
In 2006, researchers at Emory University School of Medicine found evidence to suggest that the inflammatory response to stress is greater in people prone to depression. This is just one line of evidence in the inflammation/depression link. Deans (2011) also points to the evidence that young and old people with depression have elevated levels of inflammatory proteins in plasma and cerebrospinal fluid. Other evidence points to interferon treatments which cause an increase in inflammatory proteins in the body. Depression is a known outcome of interferon. People with inflammatory diseases such as rheumatoid arthritis, insulin resistance and cardiovascular disease have higher rates of depression too.
Our bodies are designed to produce an inflammatory response to bacterial and viral infections. Some forms of influenza produce very clear signs of this response as we react with a high temperature and fever. A less extreme example, for instance of increasing an inflammatory response through diet, is much less well known. But exactly what the mechanism is that links inflammation to depression is less certain.
The brain and the immune system are connected so a change in one affects the other. Various hormones in the immune system, known as cytokines, and inflammatory proteins are positively correlated with depression. In layman's terms, the more depression there is the more inflammation there is. Following the logic, it stands to reason that by decreasing inflammation we should be able to decrease depression and there is some evidence to support this theory (Hedaya 2009).
In an interesting blog by Emily Deans, M.D. the issue of food, and specifically omega 3 and 6 fatty acids is a focus. Deans points out that in the U.S. at least seven percent of calories come from omega 6 fatty acids. There is a case, she suggests, for reducing our intake to less than four percent (hunter gatherers she points out consume less than one percent of calories from omega 6 fatty acids). In what Dean describes as the "vegetable oil" theory, she states we are predisposed to inflammation by the relative imbalance between anti-inflammatory omega 3 fatty acids (fish oil) and omega 6 fatty acids (vegetable oil). Omega 6 fatty acids are the precursors to cytokines mentioned previously. So, shift the balance in favor of omega 3 and good things should start to happen. In the largest study yet, Dean points out, a daily dose of 150mg DHA and about 1000 EPA (the components of fish oil) shows benefits equal to a prescription antidepressant.
In closing this Sharepost I'd like to borrow a comment from Robert Hedaya, M.D., who likens inflammation to a smoldering fire. "When you treat it, it can take several months for the fire to go out. But the juice is worth the squeeze, you will not only have less depression, but your risk for a host of other diseases will go down."
Deans, E. Depression - Caused by Inflammation, Thus Like Other Diseases of Civilization. Psychology Today. http://www.psychologytoday.com/node/57915 Mar 31, 2011
Hedaya, R. Depression, Inflammation, Immunity and Infection. Psychology Today. http://www.psychologytoday.com/node/4106. Mar 31 2009
Nauert, R. Depression, Stress, Inflammation and Disease. Psychcentral.com. http://psychcentral.com/news/2006/09/02/depression-stress-inflammation-and-disease. Sept 2, 2006