Last updated February 27, 2018 at 1:44 pm
Discovery of raised inflammation could lead to new treatments.
People with longer periods of untreated depression over a decade had significantly more brain inflammation compared to those who had less than 10 years of untreated depression.
It suggests that depression may be progressive, rather than a static condition. Despite depression not being a neurodegenerative disease, it draws parallels with degenerative brain diseases such as Alzheimer’s and Parkinson’s disease which are associated with brain inflammation and which their status can change over time.
Senior author Dr. Jeffrey Meyer says that this study provides the first biological evidence for large brain changes in long-lasting depression, suggesting that it is a different stage of illness that needs different therapeutics – the same perspective taken for early and later stages of Alzheimer’s disease.
Long-term depression changes the brain
Brain inflammation was determined by brain imaging with positron emission tomography (PET).
Migroglia – immune cells in the brain – are part of the brain’s typical inflammatory response to trauma or injury, however, too much inflammation is associated with degenerative diseases as well as depression.
When microglia are activated, they make more translocator protein (TSPO), a marker of inflammation that can be seen using PET imaging. The study measured the total volume of TSPO in various brain regions.
It involved 25 people with more than 10 years of untreated depression, 25 with less than 10 years of untreated illness, and 30 people with no depression as a control group.
Study participants with untreated depression for more than 10 years had TSPO levels 29–33% greater in the brain than in participants who were untreated for nine years or less. They were also 31-39% greater than healthy participants.
They also found there was a relationship between TSPO and antidepressant exposure suggesting there could be an unexplored effect of antidepressants on microglial activation.
Antidepressants and treatment options for depression
This research comes out after The Lancet last week published a comprehensive study of more than 120,000 people that showed that antidepressants work better than placebos.
Treatment options for this later stage of illness, such as medications targeting inflammation, are being investigated by Dr. Meyer and others. This includes re-purposing current medications designed for inflammation in other diseases to be used in major depressive disorder.
Previous research lead by Meyer, published in JAMA Psychiatry, found that a biomarker associated with brain inflammation was increased by 30 per cent in people with clinical depression. It was the first time it was shown in the brain.
This research was published in The Lancet Psychiatry.