New biological evidence reveals link between brain inflammation and major depression

January 28, 2015

A new study by the Centre for Addiction and Mental Health (CAMH) found that the measure of brain inflammation in people who were experiencing clinical depression was increased by 30 per cent. The findings, published today in JAMA Psychiatry, have important implications for developing new treatments for depression.

"This finding provides the most compelling evidence to date of brain inflammation during a ," says senior author Dr. Jeffrey Meyer of CAMH's Campbell Family Mental Health Research Institute. "Previous studies have looked at markers of inflammation in blood, but this is the first definitive evidence found in the brain."

Specifically, Dr. Meyer's research team was able to measure the activation of immune cells, known as microglia, that play a key role in the brain's inflammatory response.

To investigate whether brain inflammation was increased in people during clinical depression, Dr. Meyer and his team conducted brain scans on 20 patients with depression but who were otherwise healthy and 20 healthy control participants using a brain imaging technique called (PET). Results showed a significant elevation of brain inflammation in participants with depression. Rates of inflammation were also highest among those with the most .

Although the process of inflammation is one way that the brain protects itself - similar to the inflammation of a sprained ankle—too much inflammation may not be helpful and can be damaging. A growing body of evidence suggests the role of inflammation in generating the symptoms of a major depressive episode such as low mood, loss of appetite, and inability to sleep. But what was previously unclear was whether inflammation played a role in independent of any other physical illness.

"This discovery has important implications for developing new treatments for a significant group of people who suffer from depression," says Dr. Meyer, who also holds a Canada Research Chair in the neurochemistry of . "It provides a potential new target to either reverse the or shift to a more positive repair role, with the idea that it would alleviate symptoms."

The drive to uncover new ways to target and treat depression is fueled by the reality that more than half of people with major depression do not respond to antidepressant treatments and four per cent of the general population is the midst of a clinical episode. Current treatments do not target inflammation, and treating with anti-inflammatories is one avenue for future research, Dr. Meyer says.

"Depression is a complex illness and we know that it takes more than one biological change to tip someone into an episode," says Dr. Meyer. "But we now believe that inflammation in the brain is one of these changes and that's an important step forward."

First author of the study was post-doctoral research fellow Dr. Elaine Setiawan. This research was supported by the Canadian Institutes of Health Research, the Brain and Behavior Research Foundation, the Canada Foundation for Innovation and the Ministry of Research and Innovation.

Explore further: Brain protein may explain depression in pre-menopausal women

Related Stories

Uncovering the source of inflammatory malaise

October 22, 2012

(Medical Xpress)—A study conducted by researchers at Emory indicates that inflammation targets a part of the brain called the basal ganglia, causing symptoms of depression and fatigue. The study was recently reported in ...

Inflammation in depression: Chicken or egg?

January 5, 2012

An important ongoing debate in the field of psychiatry is whether inflammation in the body is a consequence of or contributor to major depression. A new study in Biological Psychiatry has attempted to resolve the issue.

Recommended for you

Study shows there's a positive side to worrying

April 27, 2017

Worry - it does a body good. And, the mind as well. A new paper by Kate Sweeny, psychology professor at the University of California, Riverside, argues there's an upside to worrying.

Study links cannabis use in adolescence to schizophrenia

April 26, 2017

Scientists believe that schizophrenia, a disorder caused by an imbalance in the brain's chemical reactions, is triggered by a genetic interaction with environmental factors. A new Tel Aviv University study published in Human ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.