Brain Inflammation Linked to Depression

Canadian researchers with the Centre for Addiction and Mental Health (CAMH) have been studying the effects of depression on the brain and have found that inflammation in the brain is elevated in those with depression. They also discovered that for people who have longer periods of untreated depression (more than a decade), there is significantly more brain inflammation.1,2

Physical evidence of inflammation in the brain

The first study looked at inflammatory markers in the brain: specifically, they measured the number of microglia cells that were activated. Microglia play a key role in the inflammation response in the brain, and when they are activated, they make more of a protein called translocator protein (TSPO). TSPO can be viewed using brain scans with positron emission tomography (PET). The researchers conducted brain scans on 20 people with depression and 20 healthy control subjects and found that those with depression had an increase in brain inflammation by about 30%. The inflammation was greatest among those who had the most severe depression.1,2

Long-term effects of untreated depression

The latest study by CAMH also used brain imaging and looked at 25 people with more than 10 years of depression, 25 people with less than 10 years of depression, and 30 people with no depression. The TSPO levels (indicating activated microglia) were 30% higher among those with 10 years or more of untreated depression compared to those with shorter periods of depression.2

About inflammation and depression

While inflammation can be a protective mechanism of the body, such as when a sprain causes inflammation to immobilize the joint, chronic inflammation can cause damage to surrounding tissues. Chronic brain inflammation is associated with other degenerative diseases including Alzheimer’s disease and Parkinson’s disease.1,2

Data from several research studies suggests that the role of inflammation in depression might be responsible for symptoms like low mood, loss of appetite, and difficulties with sleep. As of now, it’s unclear whether inflammation is the cause of depression and its symptoms, or if inflammation of the brain is a symptom of depression.1

A new treatment target

This research on inflammation is important because more than half of people with depression do not get relief with antidepressants. Antidepressants do not target inflammation. Identifying inflammation as a major characteristic of depression – whether inflammation is the cause of depression or a symptom – provides a new potential target for treatment approaches.1,2

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