The Mechanism Of Over-general Autobiographical Memory On Suicidal Ideation Of Depression Patients

Objective:There are more than 322 million people with depression worldwide,of which65%?80%have suicidal ideation,45%?55%have suicidal or self-injury behavior,and the probability of lifelong suicidal ideation is as high as 15%?25%.Suicidal behavior is a complex and progressive process:individuals are over-sensitive to the environment,which triggers suicidal ideation,makes suicidal attempts,and finally results in suicide.Suicidal ideation is the start of suicidal behavior.Intervention at this stage can effectively reduce suicidal behavior.Behavioral research shows that over-general autobiographical memory is the main risk factor of suicidal ideation,which promotes the change of sense of failure and humiliation into suicidal ideation and intermediates suicidal behavior.However,at present,there is a lack of research on brain structures and functions,leading to difficultly clarify the specific mechanism of their effect on suicidal ideation.Therefore,this study will take depression suicidal ideation as a classified variable and over-general autobiographical memory as the research goal,and will collect brain waves and neural network signals during behavioral experiments to study the changes of brain structures and brain functions related to over-general autobiographical memory in depression,and eventually to provide reference and basis for clinical prevention,diagnosis and treatment of suicidal ideation in depression patients.Methods:180 subjects with depression and 176 healthy subjects were measured by behavioral scale.Through the multi-group path analysis of structural equation model,the effect of over-general autobiographical memory on suicidal ideation between patients with depression and healthy people was detected.Then,29 normal subjects,25 depression subjects without suicidal ideation and 20 depression subjects with suicidal ideation were selected for behavioral scale measurement and autobiographical memory test under the condition of synchronous EEG-fMRI.The differences of behavior,magnetic resonance imaging and electroencephalogram data of the three groups were analyzed to clarify the mechanism of over-general autobiographical memory in suicidal ideation of depression.Results:(1)Childhood trauma can promote the production of current suicidal ideation.Over-general autobiographical memory and the worst-point suicidal ideation play an intermediary role,which directly affects the current suicidal ideation(?~2/df=2.127,CFI=1.00,TLI=0.98,NFI=0.99,RMSEA=0.056,P=0.12).Over-general autobiographical memory was positively correlated with current suicidal ideation and worst-point suicidal ideation in the depression group(r=0.384,0.214,Ps<0.01),but only positively correlated with the worst-point suicidal ideation in the healthy control group(r=0.235,P<0.01).Only in the depression group,overgeneral autobiographical memory played an intermediary role in childhood trauma and current suicidal ideation(z=-2.342,P<0.05).(2)In the autobiographical memory test,the scores of general memory and reaction time in memory construction stage of depression patients with suicidal ideation were significantly higher than those of non-suicidal ideation group and normal control group(F=12.666?114.049,Ps<0.001),and the score of general memory was higher than that of specific memory in suicidal ideation group(t=-12.403,P<0.001).In the aspect of recalling emotion,there was a significant increase in negative emotional memory in the general memory of suicidal ideation group(?~2=24.840,P<0.001).From the perspective of recall scene,the suicidal ideation group was more likely to recall the events in the last year than the non-suicidal ideation group(?~2=30.022?52.384,Ps<0.001).(3)The density of gray matter in the left supramarginal gyrus(BA40)in the normal control group was significantly higher than that in both the non-suicidal intention group(t=4.20,P<0.001)and the suicidal ideation group(t=4.75,P<0.001).The density of gray matter in the left supramarginal gyrus was negatively correlated with the degree of depression,suicidal ideation,past suicidal behavior and childhood trauma(r=0.282?0.517,Ps<0.05),and positively correlated with the specific memory score of autobiographical memory test.The more over-general autobiographical memory is,the lower the density of gray matter is in the left superior marginal gyrus(r=0.599,P<0.05).(4)In the resting state,the functional connections of the medial superior frontal gyrus(BA8)of the right frontal parietal network and the left middle frontal gyrus(BA9)of the somatic motor network in the suicidal ideation group were lower than those in the non-suicidal ideation group and the normal control group(t=3.23?5.20,Ps<0.01).The connection strength between the right hippocampus and the left inferior parietal angular gyrus in the non-suicidal ideation group was lower than that in the normal control group and suicidal ideation group(t=3.06?3.75,Ps<0.01).The normalized shortest path in the suicidal ideation group was significantly lower than that in the normal control group(t=2.65,P<0.05).The node attributes of left medial superior frontal gyrus,right caudate nucleus,left thalamus,left dorsolateral superior frontal gyrus,left middle occipital gyrus,left superior parietal gyrus,right superior parietal gyrus,left inferior temporal gyrus,left fusiform gyrus and right fusiform gyrus decreased in patients with suicidal ideation,while the node attributes of right cuneiform lobe,left dorsolateral superior frontal gyrus and right medial superior frontal gyrus were increased(F=3.17?4.47,Ps<0.05).The phase delay index of C3-P3 lead in depression patients with suicidal ideation was significantly lower than that in patients without suicidal ideation(P<0.05).(5)During the construction stage of autobiographical memory retrieval,the activation intensities of left medial superior frontal gyrus(BA32),left calcarine(BA30)and left middle frontal gyrus(BA6/9)in suicidal ideation group was lower than that in normal control group and non-suicidal ideation group.The activation intensities of these three brain regions were negatively correlated with the degree of depression,suicidal ideation and previous suicidal behavior(r=0.235?0.429,Ps<0.05).The activation intensity of the left calcarine was positively correlated with the specific memory score of the autobiographical memory test(r=0.275,P<0.05).During the construction and elaboration stages of autobiographical memory retrieval,the?-band energy of the right prefrontal lobe and parietal-occipital cortex in the suicidal ideation group were significantly lower than that in the normal control group and the non-suicidal ideation group(t=2.86?3.20,Ps<0.05).Conclusion:Over-general autobiographical memory in depression can directly enhance suicidal ideation and play an intermediary role in childhood trauma and suicidal ideation.The higher level of the over-general autobiographical memory,the longer the construction stage,the more likely suicide ideation will be generated in depression patients.The density of gray matter in the brain structure of the left superior marginal gyrus decreased,the functional connections of the left prefrontal lobe,right hippocampus,right caudate nucleus,bilateral superior parietal gyrus and bilateral fusiform gyrus decreased in the resting brain network,the activation intensity of left medial frontal gyrus,left peri-talar fissure cortex and left middle frontal gyrus decreased,and the?-band energy of right prefrontal lobe and parietal occipital cortex decreased during autobiographical memory extraction,which might be the neural basis of suicidal ideation in depression.