New research finds that patients with major depressive disorder (MDD) have increased levels of brain cell inflammation.
Importantly, researchers at the University of Manchester discovered that the inflammation was present only in patients with MDD who were experiencing suicidal thoughts.
This link suggests nerve cell inflammation, rather than a diagnosis of MDD, is associated with suicidal thoughts. The research, led by Dr. Peter Talbot and colleagues appears in the journal Biological Psychiatry.
“Our findings are the first results in living depressed patients to suggest that this microglial activation is most prominent in those with suicidal thinking,” said Dr. Talbot. Previous studies suggesting this link have relied on brain tissue collected from patients after death.
“This paper is an important addition to the view that inflammation is a feature of the neurobiology of a subgroup of depressed patients, in this case the group with suicidal ideation,” said Dr. John Krystal, Editor of Biological Psychiatry.
“This observation is particularly important in light of recent evidence supporting a personalized medicine approach to depression, i.e., that anti-inflammatory drugs may have antidepressant effects that are limited to patients with demonstrable inflammation.”
In the study, first author Dr. Sophie Holmes and colleagues assessed inflammation in 14 patients with moderate-to-severe depression who were not currently taking any antidepressant medications.
Immune cells called microglia activate as part of the body’s inflammatory response, so the researchers used a brain imaging technique to measure a substance that increases in activated microglia.
The evidence for immune activation was most prominent in the anterior cingulate cortex, a brain region involved in mood regulation and implicated in the biological origin of depression. This finding confirmed the results of a previous study that identified altered microglial activation in medication-free MDD patients. Smaller increases were also found in the insula and prefrontal cortex.
“The field now has two independent reports — our study and a 2015 report by Setiawan and colleagues in Toronto — showing essentially the same thing: that there is evidence for inflammation, more specifically microglial activation, in the brains of living patients during a major depressive episode,” said Dr. Talbot.
This link suggests that among depressed patients, neuroinflammation may be a factor contributing to the risk for suicidal thoughts or behavior.
According to Dr. Talbot, the findings “emphasize the importance of further research into the question of whether novel treatments that reduce microglial activation may be effective in major depression and suicidality.”