Although neurobiological research has pushed for determining biomarkers of major depressive disorder (MDD), the test-retest reliability of functional connectivity resting-state magnetic resonance imaging (fc-rsMRI) has not been assessed. Individuals with MDD and those in remission from MDD typically show increased fc-rsMRI within the default mode network (DMN), characterized as a set of regions coordinated in activity during mind-wandering or rest. Evidence in MDD also suggests aberrant connectivity between the DMN and cognitive control network (CCN) responsible for task- and attention-switching. Thus, a reliable within-DMN and between-network connectivity may provide an opportune window for further exploring depression etiology. The current study examined correlations of spontaneous blood oxygen level dependent activity both within the DMN (ventral and core DMN subcomponents) and between-networks (DMN – CCN subcomponents) over two time points in 82 individuals either with remitted (r) MDD (n = 47) or as Healthy Controls (HC; n = 35) to further classify the reliability of the networks and abnormalities in MDD. Linear Mixed Effects (LMEs) models showed that rMDD have a stable hyperconnectivity within DMN subcomponents and between cDMN and CCN subcomponents, but show no abnormality between vDMN and CCN subcomponents. In addition, rMDD showed more reliable connectivity over time than healthy controls, suggesting these network correlations are stable disease markers. The specificity of these findings has implications for future examinations of malleable treatment targets (i.e., vDMN – CCN connectivity) and stable disease markers that can identify those most at risk for developing the disorder (i.e., cDMN – CCN connectivity)
