Resting-State Functional Connectivity of the Hippocampus in Suicide Ideal Patients with Major Depressive Disorder

Objective:Suicide is highly-prevalent and the most serious outcome in major depressive disorder（ MDD）,yet the disturbances in neural functional system that confer suiciderisk remain obscure. In this study,we seek to investigate the neural functional differences between healthy participants with suicidal ideal（ SI） MDD patients. Methods:Seventy-seven healthy controls（ HC） and 124 well-matched MDD patients with different degrees of SI were recruited. Based on suicide factors of 17-items Hamilton Depression Scale（ HAMD-17）,We divided MDD patients into four groups,MDD;（ n=55）,MDD patients without SI;MDD;（ n=41）,MDD patients with mild SI,MDD;（ n=20）,MDD patients with moderate SI,MDD;（ n=8）,MDD patients with severe SI. Bilateral hippocampus were selected to construct hippocampus memory functional connectivity networks（ HFCN）. One-way ANCOVA was applied to investigate the difference in HFCN between different level of SI patients with MDD and HC. Furthermore,the correlation analyses were conducted to identify the correlation between HFCN and HAMD-17 scores in the SI groups. Results:Compared with CN subjects,MDD patients showed severer SI. We found significant group differences on the bilateral HFCN in bilateral supramarginal gyrus（SMG）,right middle prefrontal cortex（ mPFC）,orbital frontal cortex（ OFC）,angular cortex,as well as left middle temporal gyrus（ MTG）,superior parietal gyrus（ SPG）,and precuneus. Interestingly,an inverted U-shaped modulation was showed in the right mPFC（ control system）,right IPG,left SPG and SMG,while U-shaped modulations were found in the right hippocampus. The correlation analysis showed a significant correlation between the HAMD-17 scores and functional connectivity of the right hippocampus with the right mPFC area in the SI groups（r=-2.12,P=0.018）. Conclusion:Our study manifested a nonlinear modulation of interacting between suicide ideal and depression on brain function. These findings expand our understanding of the functional neural basis of different level of SI in MDD patients and will help to reveal the pathophysiology underlying suicidality in patients with MDD.