The Add-on Role of Deeb-Transcranial Magnetic Stimulation on Clinical Symbtoms and Cognitive Function in Major Debressive Disorders and Its Electroencephalograbhic Mechanism
Objective: Depression is a disabling psychiatric disorder with a high prevalence and is often associated with cognitive impairment, making patients' recovery more difficult. Currently, depression is mainly treated clinically with medications, which have limitations including side effects and little efficacy on improving cognitive functions. In recent years, non-invasive brain stimulation techniques have been gradually applied in clinical practice, among which deep transcranial magnetic stimulation (dTMS) has the characteristics of deep depth and wide range with few side effects and excellent efficacy. This study aimed to investigate the efficacy of dTMS on improving clinical symptoms and cognitive functions in patients with depression, and the brain electrophysiological mechanism underlying its efficacy.
Methods: This study included three sub-studies, which explored the cognitive function and electrophysiological characteristics of depression itself, the clinical and cognitive efficacy of dTMS, and the brain electrophysiological mechanisms underlying the efficacy of dTMS, respectively. Study I was cross-sectional and compared clinical symptoms, cognitive function, and brain electrophysiological data between patients with depression and healthy controls. Study II used a clinically randomized controlled experimental design in which the included patients were randomly divided into a dTMS real-stimulation group and a sham-stimulation group, and their clinical symptoms and cognitive functions before and after treatment were compared to illustrate the efficacy of dTMS. Study III was conducted on the basis of Study II and compared the brain electrophysiological features of the real- and sham-stimulation groups to investigate the underlying mechanisms of dTMS in treating depression and improving cognitive impairment.
Results: Study I found significant deficits in cognitive function and alterations in the values of TMS一evoked potentials (TEP) in patients with depression, with the changes in TEP being significantly correlated with clinical symptoms and impairment of cognitive function in patients. Study II found a significant decrease in depressive symptoms and anxiety symptoms and a significant increase in cognitive functions in the real-stimulation group after ten sessions of dTMS treatment. Study III found that dTMS intervention had a significant modulating effect on the N100 amplitude and P180 amplitude of TEP, and the changes of these amplitudes were associated with the improvement of patients' clinical symptoms. Moreover, the changes of several characteristic values of TEP in patients were significantly associated with the improvement of cognitive functions, especially immediate memory functions.
Conclusion: DTMS can effectively relieve clinical symptoms and improve cognitive functions in patients with depression. The brain electrophysiological mechanism underlying dTMS involves the modulation of excitatory and inhibitory mechanisms in the brain, which may be related to the relief of depressive symptoms, anxiety symptoms and cognitive impairment.
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