Andrew H. Miller, MD, a professor of Psychiatry and Behavioral Sciences at Emory University School Medicine and senior author of the trial, commented: "Inflammation is the body's natural response to infection or wounding. However, when prolonged or excessive, inflammation can damage many parts of the body, including the brain."
Previous studies have claimed that individuals with depression who have high inflammation are not as likely to benefit from common treatment, such as anti-depressant drugs and psychotherapy, which tend to help other depressed patients.
The researchers' goal with this new study was to determine if stopping inflammation could help a large spectrum of people whose depression is hard to treat, or only individuals who have high inflammation levels.
During the trial, the experts used infliximab, a biological drug recently manufactured with the intent to fix inflammatory diseases such as inflammatory bowel disease and autoimmune diseases, including rheumatoid arthritis.
Biological drugs mimic the way that substances made by the body's immune system work. Infliximab works by blocking tumor necrosis factor (TNF), which is involved in inflammation and has been found to be higher in certain depressed patients.
The people involved in the study all suffered from severe depression and did not benefit from common treatment options. They were given either a placebo or the infliximab.
At first, the researchers did not see a large difference in the improvement of symptoms in the participants who were given the placebo and the ones who were given the infliximab. However, after further investigation of the people with high inflammation individually, the authors noticed that they benefitted much more from the infliximab than the placebo.
"The prediction of an antidepressant response using a simple blood test is one of the holy grails in psychiatry. This is especially important because the blood test not only measured what we think is at the root cause of depression in these patients, but also is the target of the drug."
Charles L. Raison, MD, first author of the study and associate professor in the Department of Psychiatry at the University of Arizona College of Medicine, concluded: "This is the first successful application of a biologic therapy to depression. The study opens the door to a host of new approaches that target the immune system to treat psychiatric diseases."