Major depression not responding to standard therapy may be treated using a drug commonly prescribed for inflammation, a new study says.

Previous research has shown that depression ups the levels of inflammation markers in the body.

"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," said Andrew H. Miller, MD, professor Emory University School of Medicine and lead author of the study.

Medical Daily had earlier reported other research suggesting that depression might have evolved to enhance immune response towards diseases.

The present study included approximately 60 people with major depression; 37 of them were on antidepressants. All the participants had treatment resistant depression meaning that their depression wasn't responding to any medication. Their inflammation levels were measured by blood test for C-reactive protein (CRP) which is an inflammatory marker.

The level of CRP in the body is directly proportional to the levels of inflammation. All participants were randomly assigned to either receive the inflammation drug infliximab or a placebo.

Researchers found that participants with high levels of inflammation showed greatest improvement when treated with infliximab. The drug is designed to treat rheumatoid arthritis and inflammatory bowel disease. It acts against the protein tumor necrosis factor (TNF), a key molecule in inflammation.

"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," said Miller.

"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," added Charles L. Raison, MD, first author of the study.

The study was published in the journal Archives of General Psychiatry.