Major depressive disorder (MDD) is common and disabling, but its neuropathophysiology remains unclear. Most studies of functional brain networks in MDD have had limited statistical power and data analysis approaches have varied widely. The REST-meta-MDD Project of resting-state fMRI (R-fMRI) addresses these issues. Twenty-five research groups in China established the REST-meta-MDD Consortium by contributing R-fMRI data from 1,300 patients with MDD and 1,128 normal controls (NCs). Data were preprocessed locally with a standardized protocol before aggregated group analyses. We focused on functional connectivity (FC) within the default mode network (DMN), frequently reported to be increased in MDD. Instead, we found decreased DMN FC when we compared 848 patients with MDD to 794 NCs from 17 sites after data exclusion. We found FC reduction only in recurrent MDD, not in first-episode drug-naïve MDD. Decreased DMN FC was associated with medication usage but not with MDD duration. DMN FC was also positively related to symptom severity but only in recurrent MDD. Exploratory analyses also revealed alterations in FC of visual, sensory-motor, and dorsal attention networks in MDD. We confirmed the key role of DMN in MDD but found reduced rather than increased FC within the DMN. Future studies should test whether decreased DMN FC mediates response to treatment. All R-fMRI indices of data contributed by the REST-meta-MDD consortium are being shared publicly via the R-fMRI Maps Project.

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Background: The COVID-19 outbreak has brought tremendous psychological pressure to the general population, which may lead to depression. Therefore, this study aim to evaluate the prevalence and clinical correlates of depressive symptoms in the general population quarantined during the COVID-19 outbreak in Shenzhen. Methods: 2237 quarantined general individuals participated in this cross-sectional study from February 14 to March 4, 2020, during their 14 days quarantine. They completed the Zung's Self-Rating Depression Scale (SDS) for depression, Zung's self-rating anxiety scale (SAS) for anxiety, the Pittsburgh Sleep Quality Index (PSQI) for sleep quality, and the Impact of Events Scale-Revised (IES-R) for post-traumatic stress symptoms (PTSS). Results: The prevalence of depressive symptom was 6.21% in quarantined individuals. The depressed group were younger, less married and educated, and had higher SAS, PSQI, IES-R total scores (all p<0.05), as well as more avoidance, intrusion and hyperarousal symptoms than the non-depressed group. Correlation analysis showed significant correlations between SDS score and the following parameters: age, marriage, education, SAS, PSQI, IES-R total and its three subscale scores (Bonferroni corrected all p<0.05). Further multiple regression indicated that age, marriage, education, SAS, PSQI, IES-R total score, Avoidance and Hyperarousal factor were independent predictors of depressive symptom. Limitations: This study adopted a cross-sectional design and used self-report questionnaires. Conclusions: Our results suggest an elevated prevalence of depressive symptom in quarantined general individuals in Shenzhen. Some demographic and clinical variables were associated with depressive symptoms.