Looking closely: Inflammation imaging as a depression biomarker
Does depression cause inflammation or does inflammation cause depression? There seems to be another vote for inflammation as a root cause with research published in The Journal of Nuclear Medicine. In a cross-disciplinary study at the Yale School of Medicine, researchers from the radiology and psychiatry departments looked at how the moods of volunteers responded to inflammation triggered by an endotoxin, and they found a possible imaging biomarker.
Dosing people with an endotoxin sets up inflammation throughout the body, and with this, some mild symptoms of depression--for example, tiredness and lack of interest--thus, it can be used to look at the responses in the brain. The researchers used PET imaging in people at rest (so they knew the changes could only be from the inflammation) and saw changes in the way the regions called the insula and cingulate used glucose. These brain regions are involved in interoception (knowing how the body feels), positive emotional feelings, and motivation.
This study only evaluated 9 people; therefore, the results need to validated in a much bigger group. Furthermore, researchers also need to evaluate people who have clinical depression, rather than a model of depression caused by an endotoxin. However, if studies could show that a subtype of depression is caused by inflammation, this could be a target for treatments (for example, reducing inflammation in patients where this plays a role).
"In the future, I expect that researchers in this field will be able to develop more precise PET measures that can be used to distinguish between, for instance, a person with 'inflammatory depression' and a person with another kind of depression. PET could then be used as diagnostic biomarker to separate subtypes of depression and as a therapeutic biomarker to detect the response to treatment," explained the article's lead author Jonas Hannestad.