| Childhood trauma refers to the traumatic experience of an individual in childhood and adolescence,including all kinds of physical or emotional abuse,neglect and sexual abuse,etc.Childhood trauma often occurs with stronger depressive mood,or even increases the incidence of Major Depression Disorder(MDD).However,a consistent conclusion about the psychological mechanisms that explain the relationship between childhood trauma and depression remain unclear.Investigating the potential influence of childhood trauma experience on subclinical depressive symptoms is helpful to propose appropriate treatment and intervention to relieve depressive symptom which caused by childhood trauma.With the rapid development of magnetic resonance technology,researchers begun to focus on the neural mechanisms of psychological variables such as cognition and emotion,as well as the influence of personal experience and environment on the development of the brain.So far,there is no consistent conclusion about the effects of childhood trauma on the brain structure and function because of the limitation of small sample size and unsystematic analytical methods in existing studies.In addition,a large number of studies have explored the relationship between childhood traumatic experience and the incidence of mental disorder and the severity of symptom.However,few studies have focused on the impact of childhood traumatic experience on negative emotions in healthy individuals.Finally,childhood trauma experience is an important risk factor for emotional disorder,but the relationship between childhood trauma,depression,and emotional processing and their corresponding neural mechanisms have not been systematically studied.Therefore,based on seven experiments in three studies,we explored the potential effects of childhood traumatic experience on subclinical depressive symptom and the underlying neural basis of their relationship.Considering that emotional processing plays a key role in the relationship between childhood trauma and depression,we furtherly explored the neural mechanism of emotion processing associated childhood trauma,which would provide a reference for future intervention research on emotional disorders caused by childhood trauma.Study 1 consists of two experiments,which were designed to explore the relationship between childhood trauma and subclinical depressive symptom and the corresponding psychological mechanism.Both cross-sectional and longitudinal method were used to explore the predictive validity of childhood trauma on depressive feeling in three samples of healthy adults,healthy adolescents,and patients with MDD.In Experiment 1,significant and positive associations between childhood trauma and depression were found in all three samples after controlling for gender,age,and current stress.Additionally,childhood trauma predicted high levels of subclinical depressive symptoms one year later.Experiment 2 aimed to explore the psychological mechanism of the influence of childhood trauma on subclinical depressive symptoms.From the perspective of emotion processing,we propose the hypothesis that childhood trauma may disturb the normal emotion process,which would increase individual’s depressive symptom when facing with stressful life event.We construct two mediation models with childhood trauma as the independent variable,subclinical depressive symptoms as the dependent variable,and emotional attention and emotional regulation as mediating variables to explain the relationship between childhood trauma and depression.The results showed that emotional attention bias mediated the relationship between childhood trauma and depression.In addition,cognitive reappraisal ability mediated the relationship between childhood trauma and depression.In sum,Study 1 indicated that childhood trauma can predict an individual’s future depression.Emotional attention bias and the ability to regulate emotion can explain the relationship between childhood trauma and depression.These results can provide a reference for developing behavioral interventions to decrease the negative effect of childhood trauma.Next,Study 2 explores the brain structural and functional basis of childhood trauma and its relationship with depression from the perspective of individual differences.Based on the results of Study 1,we focused on brain regions and networks related to emotional processing.Furthermore,the neural basis which support the association between childhood trauma and depression were explored through mediation models.In Experiment 3,a large sample of brain structural data was used to explore the brain structure related to childhood trauma using voxel-based morphometry(VBM)method.Considering the key role of amygdala in stress and emotion processing,we choose amygdala and its subregions as regions of interest(ROI)to analysis the relationship between the grey matter volume(GMV)of amygdala and childhood trauma.We verified these results on another dataset to improve the reproducibility of results.The results showed that childhood trauma was negatively related to the GMV in brain regions of bilateral hippocampus extending to amygdala,right precuneus,and right middle temporal gyrus.The above results suggested that individual with more childhood trauma experience may have stronger sensitivity of threat information and impaired retrieval of autobiographical memory.The results of the mediation analysis showed that the GMV of the left basolateral amygdala(BLA)can mediate the relationship between childhood trauma and depression.BLA was proved to be involved in the detection of threat stimulus and response,the smaller GMV in BLA might associated with increasing sensitivity to stress in later life,thus lead to higher depressive symptoms when coping with stressful events.In Experiment 4,we explored the functional connectivity of the brain networks associated with childhood trauma by extracting time series of brain regions by using the Power264 template and constructed a large-scale functional network based on resting state f MRI.The results show that childhood trauma was positively linked to within-network connectivity in ventral attention network(VAN),dorsal attention network(DAN),salience network(SN),and sensorimotor network(SMN),and was positively linked to the between-network connectivity of VAN-DAN,VAN-visual network(VN),and VAN-SMN.These withinand between-network functional connectivity may be involved in the processing of external stimuli,emotional attention and perception,which may explain greater sensitivity of negative emotional stimulus and emotional attention bias in traumatized individuals.The results showed that the within-network connection of VAN can mediate the relationship between childhood trauma and depression,which is consistent with previous findings suggesting that individuals with higher depressive symptom would have higher sensitivity towards threat stimuli.One possible explanation is that the increased connectivity within the VAN may be related to stimulus-driven attention to threatening stimuli,thus increasing depressive symptom.In summary,the results of Study 2 indicated that individual with higher childhood trauma experience would have smaller GMV in hippocampus,amygdala,right precuneus,and right middle temporal gyrus and greater between-and within network connectivity in VAN,DAN,SN and SMN.These structural and functional changes in brain may be associated with greater stress sensitivity,negative emotional attention bias and negative emotional experience.Study 1 proved that disrupted emotional attention and emotional regulation are the psychological mechanisms of the relationship between childhood trauma and depression.Study 2 investigate the neural basis of the relationship between childhood trauma and depression and the results also pointed to brain regions and networks related to emotional processing.Therefore,in Study 3,we use task f MRI to explore the neural mechanisms of the relationship between childhood trauma and depression from the perspective of emotion processing(emotion attention,emotion recognition,and emotion regulation).Experiment 5 explores the brain mechanism of emotional attention bias in traumatized individuals using the classic point detection paradigm.The results showed that stronger brain activation in the dorsolateral prefrontal cortex(DLPFC)and dorsolateral anterior cingulate cortex(d ACC)were found in trauma group compared with control group.The extracted values of brain activity in DLPFC and d ACC were positively related to the scores of childhood trauma experience.The extracted values of brain activity in d ACC were positively related to the scores of subclinical depressive symptom.Physiological and psychological interaction(PPI)analysis showed that the trauma group showed a weaker functional connection of insula and amygdala.In addition,the activation intensity of the dorsal lateral prefrontal lobe and the functional connections between the insula and the amygdala can predict individual’s depression.Previous studies have confirmed the role of DLPFC and d ACC in cognitive control and attention control.During the dot probe task,participants may need to eliminate the interference of emotional stimulus and respond to the detective stimulus quickly.The greater brain activation in DLPFC and d ACC may indicate that individual with high level of childhood traumatic experience need to exert more cognitive and attention control resources to eliminate the influence of emotional stimulus in order to complete the experimental task during the fear condition.Based on these results we infer that childhood trauma may damage the individual’s ability to control attention and prevent them from processing negative stimuli,thereby disrupting normal cognitive processes or emotional regulation processes.Therefore,traumatized individuals will experience more negative emotion when facing subsequent stressful events.In Experiment 6,we used face-matching task to explore the differences in brain activation between the trauma group and the control group during emotion recognition.We found that the trauma group showed stronger brain activation in the region of the amygdala and the d ACC compared with the control group.We also found that greater brain activation in amygdala and d ACC were related to the higher scores of childhood trauma questionnaire.The trauma group showed stronger functional connectivity between d ACC and amygdala by using PPI analysis.These results may suggest that stronger brain activation in amygdala may be related to the overreaction of negative stimulus.Stronger brain activation in d ACC and stronger connectivity of d ACC-amygdala may due to the fact that individuals with childhood trauma experience are more susceptible to negative emotion,which may require more cognitive control to complete face-matching tasks.The high sensitivity of amygdala toward negative emotion in trauma group might be a risk factor for depression.In Experiment 7,we used emotion regulation task to explore the differences in brain activation between the trauma group and the control group during emotion regulation with reappraisal strategy.The results showed that cognitive reappraisal ability mediated the relationship between childhood trauma and depression at behavioral level.The trauma group showed stronger brain activation in the orbitofrontal cortex(OFC)than the control group in the cognitive reappraisal f MRI task.In addition,the brain activation in the region of the OFC was negatively correlated with the score of childhood trauma.The PPI analysis showed that the trauma group showed stronger functional connectivity of OFC,DLPFC,posterior cingulate cortex(PCC)and amygdala.And the functional connectivity of DLPFC,PCC and amygdala can predict individual’s depression.The decreased activation in the region of OFC during the process of cognitive reappraisal in trauma group may indicated that the people with high childhood trauma experience cannot effectively use cognitive reappraisal to downregulate their negative emotions.In summary,this study suggested the childhood trauma as the robust predictor of depression and its corresponding neural mechanisms.We suggested that the key neural basis of childhood trauma includes the GMV of hippocampus,amygdala,precuneus,middle temporal gyrus,as well as the functional connectivity of VAN,DAN,SN and SMN.These brain regions and networks have suggested to be involved in the attention,processing and regulating of emotional stimulus,which indicated that individuals with high childhood traumatic experience may have defects in emotional processing and regulation,and thus leading to stronger depressive symptom when coping with stressful life events.We further verified the above findings by carrying out three f MRI studies,including emotion attention,emotion recognition,and emotion regulation,and the results confirms the dysfunction of trauma individuals in emotional processing,and the predictive role of these dysfunctions in depression.Overall,this study reveals the psychological mechanism of the relationship between childhood trauma and depressive emotion from the perspective of emotional processing,and proves the important role of emotional processing and its corresponding neural basis in the relationship between childhood trauma and depression.It can provide effective prevention strategies for reducing the negative impact of childhood trauma on individuals in the future,and can also provide theoretical support for the treatment and intervention of mental disorder caused by trauma. |
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