However, a recently published study in the journal Biological Psychiatry more specifically suggests that there may be a link between brain inflammation and suicidal thoughts.
The 2015 study found a strong link between depressive episodes and increased neuroinflammation, measured by enhanced microglial activity in the brain. Microglia are a type of immune cell located throughout the brain and spinal cord that act as the main active defense in the central nervous system.
Inspired by the study, Dr. Peter Talbot from the University of Manchester decided to investigate whether increased microglial activity is linked specifically to suicidal thoughts.
Talbot's study analyzed the brains of 14 patients with moderate-to-severe depression and suicidal ideation and 13 subjects who did not report depression or such thoughts. The researchers used PET scans, which employ radiation to measure translocator protein (TSPO) levels to activate the microglia.
The results reveal that there is a strong correlation between people with suicidal thoughts and enhanced neuroinflammation.
Microglial activity was mostly increased in the anterior cingulate cortex of the depressed patients, the part of the brain responsible for mood regulation. To a lesser degree, they also showed increased inflammation of the insular cortex, which helps regulate emotional function, and of the prefrontal cortex, responsible for cognitive processes related to behavior.
Brain studies of dead suicidal patients have shown increased inflammation in the same regions of the brain.
"Our findings are the first results in living depressed patients to suggest that this microglial activation is most prominent with those with suicidal thinking," Talbot said.
Dr. John Krystal, the editor of Biological Psychiatry, commented on the significance of this observation in the field of depression. "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," Krystal said.
According to the National Institute of Mental Health, suicide is the 10th leading cause of death in the US.
