Brain Mechanisms Of Cognitive Behavioral Therapy For Mild To Moderate Depression

Major Depressive Disorder(MDD)is a common mental illness with a range of emotional and cognitive problems such as low mood and slow thinking,which are closely related to the abnormal structure and function of the brain.Cognitive behavioral therapy(CBT)is a kind of psychosocial intervention method aimed at helping individuals to change bad cognition,establish new cognitive model and improve patients' emotion.It has been widely used in the treatment of mild and moderate depression.At present,many studies have explored the brain mechanism of CBT on MDD.However,the neural mechanisms of CBT are still unclear,especially the effects of early CBT on regional and large-scale brain connectivity in MDD patients.In this study,patients with first-episode mild to moderate depression were targeted to explore the changes in brain function and structure before and after 6-week CBT,so as to further explore the underlying neurological basis of depression and the neurological mechanism of early CBT on depression.In this study,patients meeting the DSM-IV criteria for depression were selected as the experimental group for 6 weeks of cognitive behavioral therapy.The treatment process includes belief discussion,cognitive reconstruction and behavioral training.According to the gender,age,education level and other factors to choose the matched normal people as the control group.Evaluation of the Hamilton Depression Scale(HAMD)and resting state magnetic resonance imaging were performed before and after treatment.Then,the data of the following steps were analyzed before treatment,after treatment and in healthy control group:Study one: Explore the abnormality of cortical structure of MDD patients by using Surface-based morphometry analysis;Study two: Seed-based functional connectivity was used to explore the pathophysiological mechanism of MDD;Study three: Explore the neural mechanism of CBT on MDD based on Surface-based morphometry analysis;Study four: Explore the neural mechanism of CBT on MDD based on static and dynamic functional connectivity of dorsolateral prefrontal cortex(dl PFC).The results showed:(1)The results of surface-based morphometry analysis showed that,compared with the normal control group,the brain regions with aberrant cortical thickness in MDD patients included superior marginal gyrus,cingulate gyrus,postcentral gyrus and insula.Patients with MDD showed aberrant fractal dimension in dl PFC,precuneus and lingual gyrus.In addition,correlation analysis found that the cortical thickness of dl PFC was negatively correlated with the duration of MDD.The fractal dimension dl PFC was negatively correlated with the HAMD scores.(2)Functional connectivity(FC)analysis of the habenula found that MDD patients showed abnormal connectivity between habenula and the right dl PFC,compared with normal controls.There was a significant positive correlation between the FC of habenal and dl PFC and HAMD scores.(3)After cognitive behavioral therapy,cortical thickness changed in brain areas mainly included dl PFC,posterior cingulate gyrus,insula and parahippocampal gyrus,while fractal dimension changed in corpus callosum and precentral gyrus.(4)The results of degree centrality showed that after CBT,the degree centrality value of left dl PFC was increased.Correlation analysis found that degree centrality of the left dl PFC was negatively correlated with the duration of patients with MDD.The results of static functional connectivity revealed that after CBT,the FC between the dl PFC and right hippocampus was enhanced.The results of dynamic functional connectivity revealed that after CBT,the dynamic functional connectivity between the dl PFC and precuneus were enhanced.Patients with first mild to moderate MDD showed cortical structural and function damage,which was mainly distributed in the cortex-limbic system and other neural circuits that are closely related to emotion and cognition.The dl PFC plays an important role in the pathophysiological mechanism of MDD.CBT improved the connectivity between dl PFC and hippocampus of MDD patients,suggesting that CBT can improve the depressive symptoms by changing the function of the cortex-limbic neural circuit.The functional connectivity between the dl PFC and the default mode network was improved,suggesting that CBT treatment could increase the reactive inhibition ability and promote the recognition and processing of negative emotion and negative thinking.As a key node involved in cognitive control,dl PFC plays an important role in the influence mechanism of CBT on depression.The early stage of CBT treatment can improve the key abnormal brain mechanism of MDD.