Most of the patients diagnosed with depression are more susceptible to infections and other inflammatory diseases, which increases inflammatory markers levels in the bloodstream. A team of psychiatrists from the Emory University School of Medicine and Winship Cancer Institute, have recently discovered a link between high levels of inflammatory markers and a persistent symptom of depression called anhedonia.
Anhedonia is difficult to treat symptom of depression as it represents the inability of feeling any pleasure towards everything that brought the patient pleasure before facing depression. The study lead by PhD Jennifer Felger, consisted of a group of 48 depressed patients from whom blood samples were taken to measure their C-reactive protein (CRP), one of the most common inflammatory marker. With the help of a functional-MRI, they were able to see that patients with high levels of CPR, had almost no communication between two important brain regions that are responsible with rewarding pleasurable activities and motivation.
Apparently, the lack of this functional communication appears only in patients with increased levels of CRP, meaning that inflammation anywhere in the body might determine anhedonia in depressed people. What is even more interesting is that, they’ve also discovered a slower motor function in depressed patients with anhedonia because of a low connectivity between other two regions of the brain.
“Our data suggest that by blocking inflammation or its effects on the brain, we may be able to reverse anhedonia and help depressed individuals who fail to respond to antidepressants.” Said Jennifer Felger, who is now trying to test if a drug called L-DOPA might stabilize the connectivity in the brain that seems to be lost in depressives with anhedonia. L-DOPA is actually a precursor of dopamine, a neurotransmitter that seems to be reduced when inflammations are involved.
All in all, this remarkable study brings more insight on the chemical effect on the brain during depression and might even differentiate depression from anhedonia. Also, it reveals that inflammation might be responsible for hard to treat depression.