Inflammation In Brain May Be A Cause Of Severe Depression

Inflammation is the immune system's natural response to infection or disease. The body often uses inflammation to protect itself, such as when an ankle is sprained and becomes inflamed, and the same principle also applies to the brain. However, too much inflammation is unhelpful and can be damaging.

Increasingly, evidence is suggesting that inflammation may drive some depressive symptoms, such as low mood, loss of appetite and reduced ability to sleep.

Researchers from the Centre for Addiction and Mental Health's (CAMH) Campbell Family Mental Health Research Institute in Toronto, Canada, used positron emission tomography (PET) to scan the brains of 20 patients with depression and 20 healthy control participants.

In particular, the team closely measured the activation of microglia - immune cells 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, and the inflammation was most severe among the participants with the most severe depression, The brain of people who were expecting clinical depression exhibited an inflammatory increase of 30%.

Previous studies have examined markers of inflammation in the blood of depressed people, to attempt to solve the "chicken or egg" debate of whether inflammation is a consequence of or contributor to major depression.

A study conducted by Duke University Medical Center researchers found an association between the number of cumulative depressive episodes experienced by studying the participants and increased levels of an inflammation marker in their blood called C-reactive protein (CRP).

Depression, therefore, is more likely to contribute to inflammation in the body as opposed to arising as a consequence of inflammation.