Inflammation is associated with altered functional connectivity of cingulate cortex in subthreshold depression

Motivation: Subthreshold depression (StD) as a transitional stage of depression, identifying biological markers of StD is essential to prevent depression. Goal(s): To investigate the relationship between brain function, inflammatory cytokines, and symptoms in StD. Approach: Multiple linear regression was adopted to model the relationship between functional connectivity (FC) values, psychological variables and pro-inflammatory cytokines levels of StD. Results: The interaction of Interleukin-1β (IL-1β) level × FC values in anterior cingulate cortex (ACC) - superior frontal gyrus (SFG) was an independent predictor for the anxiety scores in StD. The interaction of Interleukin-17 (IL-17) × FC in ACC - SFG was an independent predictor for the rumination scores. Impact: It is suggested that StD may have the tendency of autoimmune dysfunction. We hypothesize that IL-1β and IL-17 may show synergistic effects in inflammatory response and immune regulation, which co-influencing the FC of ACC-SFG, causing rumination and anxiety.