Background: Despite extensive research on the treatment of Major Depressive Disorder (MDD) relapse rates are as high as 80%. Of those, 30-40% fall into the severe spectrum called treatment resistant depression (TRD) as they fail to respond to at least two lines of antidepressant treatment interventions. TRD has been linked with anhedonia, the inability to experience pleasure or interest in usually enjoyable activities. The neurobiology of anhedonia is poorly understood with recent literature examining an inflammatory association and linking it to deficits in reward-related brain circuitry. The present study examines neurobiological correlates of anhedonia in MDD and TRD, specifically C-Reactive Protein (CRP), IL-6 and ventral striatal (VS) activity. The study also explores whether VS activity mediates the association between inflammation and anhedonia.
