Inflexibly sustained negative affect and rumination independently link default mode network efficiency to subclinical depressive symptoms

Aberrant DMN connectivity and activity have been robustly linked to Major Depressive Disorder (MDD) and risk for depression. This link has mostly been explained in terms of rumination, a form of negative, repetitive cognitive processing. Yet, accumulating findings are indicating altered DMN dynamics during emotional processing in MDD, pointing at a potential emotion-related DMN pathology in depression linked to inflexibly sustained emotional responses. Such a link might be especially important in understanding risk of depression. However, whether inflexible emotional processing (i.e. emotional inertia) is connecting aberrant DMN organization to risk of depression as well as how this might relate to rumination remains unclear. Addressing this gap, 34 participants underwent a resting-state fMRI and a 7-day Experience Sampling phase. Using regression and multiple mediation analysis we investigated the relations between negative emotional inertia, rumination, DMN organization and risk of depression as indicated by high subclinical depressive symptoms. The findings indicated that DMN efficiency at rest was positively associated with depressive symptoms and risk of depression. Both negative emotional inertia in daily life and rumination were independently mediating this relationship. While negative emotional inertia was connected to a broad increase in the coupling of DMN regions, rumination was only related to an increase in node strength of the dorsomedial Prefrontal Cortex. These findings are pointing towards an emotional-related DMN pathology contributing to risk of depression. Furthermore the findings are indicating that this relationship is independent from the rumination-related link between the DMN and depression - representing different aspects of DMN organization.