(Jan. 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 major depressive
episode,” 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
Dr. Jeffrey Meyer
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 positron emission tomography (PET). Results showed a significant elevation of
brain inflammation in participants with depression. Rates of inflammation were
also highest among those with the most severe depression.
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 clinical depression 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 major depression. “It provides a potential new target
to either reverse the brain inflammation 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 depression 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
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Centre for Addiction and Mental Health (CAMH) is Canada's largest mental health and addiction teaching
hospital and a world leading research centre in this field. CAMH combines
clinical care, research, education, policy development and health promotion to
help transform the lives of people affected by mental illness and addiction.
CAMH is fully affiliated with the University of Toronto, and is a Pan American
Health Organization/World Health Organization Collaborating Centre. For more
information, please visit www.camh.ca or follow @CAMHnews on Twitter.
Media Relations Specialist
Centre for Addiction and Mental Health (CAMH)
416 535-8501 ext. 36015