The Relationship Between fMRI and Symptoms of Major Depressive Disorder (CAN-BIND12)
Objective: Major depressive disorder (MDD) is a mental health issue which features a breadth of symptoms and variable presentations. Subsequently, the method of diagnosis/treatment is not one with a clear and infallible structure. The primary objective of this study is to evaluate resting-state functional connectivity and symptom severity, as determined by sleep architecture and clinical scales, in order to investigate group differences of participants currently in a major depressive episode (MDE). The secondary objective is to provide preliminary data to aid in the analysis following the unblinding of all investigators in CAN-BIND12. Methods: This was an 8-week, double blind randomized control trial. Participants were placed in two separate groups, such that mean MADRS scores did not significantly differ. Resting-state functional connectivity changes across the 8 weeks were evaluated for each group. Differences in clinical scores (mood, anxiety, and sleep quality) and sleep architecture were determined between-groups as well as within-groups. All measures were collected at baseline and week 8. Results: GROUP B displayed higher symptom severity, as seen by significantly greater MADRS and PSQI scores, compared to GROUP A. GROUP B was also the only group to show any significant changes in functional connectivity. The regions identified in the analysis have either been implicated in the Default Mode Network, the Salience Network, or sensory processing. Sleep architecture measures did not greatly differ in both the between-groups and within-groups analyses. Conclusion: The incidence of functional connectivity changes in the group with greater symptom severity across the 8 weeks, may be indicative of a relationship between whole-brain functional connectivity and depressive symptoms. Due to the fact that this difference was seen in a group solely compromised of clinically depressed individuals, fMRIs may be a useful tool when parsing through the many individual differences experienced by those with MDD. These results will also provide a basis upon which further conclusions can be made at the completion of CAN-BIND12, specifically the relationship between probiotics and functional connectivity.