Inflammation and Depression

According to a new study conducted by Canadian researchers, major depression is linked to brain inflammation. The study has been published in the magazine Archives of General Psychiatry. These findings have important implications in the development of new treatments for depression.

What is inflammation?

Inflammation is the immune system’s natural response to an infection or illness. The body often uses inflammation to protect itself. For example, when we sprain a muscle or fracture a bone, that area becomes inflamed. The same principle also applies to the brain.

However, excess inflammation can be harmful. Evidence increasingly suggests that inflammation causes some of the symptoms of depression such as low spirits, loss of appetite and trouble falling asleep.

The study

The new study aimed to investigate whether inflammation is a controlling factor for depression, independently from other physical ailments.

To investigate, the researchers used Positron Emission Tomography (PET) to scan the brains of 20 patients with depression and another 20 healthy patients. The healthy patients formed the control group.

Particularly, the team closely measured the activation of microglia, which are cells in the immune system that play a key role in the brain’s inflammatory response.

The PET scans showed significant inflammation in the brains of the people with depression. The inflammation turned out to be even more severe in the participants who suffered from more severe depression. The brains of the people that were experimenting clinical depression showed an increase in inflammation of 30%.

Previous studies

Previous studies had analyzed inflammation markers in the blood of people with depression in an attempt to see if inflammation was a consequence of the depression or if it was a factor that made depression worse.

A study, conducted in 2012 by the researchers in Duke University Medical Center in California, found a link between the number of depressive episodes experienced by the participants within the study and an increase in the levels of an inflammation marker called C-reactive protein (CRP).