Transcranial Magnetic Stimulation in Depression.

Major Depressive Disorder (MDD)

low-intensity transcranial magnetic stimulation, Major Depressive Disorder

Major depressive disorder (MDD) has increased in recent years, affecting 16.1% of the adult population nationwide. Currently, there are pharmacological and psychological treatments that have a 67% remission rate for depressive symptoms and insomnia after up to four trials of antidepressant treatments. Recently, low-intensity transcranial magnetic stimulation (Li-TMS) has been used to activate and generate structural and neural functioning changes in specific cortical regions such as the left dorsolateral prefrontal cortex, as its activity is altered in MDD. Furthermore, an increase in circulating levels of granulocytes, monocytes, and inflammatory cytokines has been observed in patients with MDD, suggesting an association between inflammation and neurotoxicity with the development of depression and decreased BDNF, mainly affecting the prefrontal cortex and hippocampus. Therefore, it has been proposed to quantify markers of systemic inflammation and evaluate their correlation with MDD and their possible effect with Li-TMS. This was a probabilistic, two-arm, block-randomized, single-blind clinical trial. A qualified psychiatrist evaluated the patients according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) to confirm the diagnosis of major depressive disorder. Two groups were formed and randomly assigned to receive treatment: transcranial magnetic stimulation or the sham group. The patients were unaware of the treatment; they did not know whether they would receive low-intensity transcranial magnetic stimulation (Li-TMS) or not. It was a clinical trial, two arms, probabilistic, block randomized, single-blind. The experimental group received conventional drug treatment combined with Li-TMS, and the control group was administered standard drug therapy with coil placement, without exposure to Li-TMS emission. Both groups had the device coils placed on them.

In low- and middle-income countries, only 25% of patients diagnosed with depression receive some form of treatment, with the current options being standard drug therapy and/or psychotherapy (WHO, 2023) (1). However, only about 35% of patients achieve complete remission of symptoms, resulting in more than half of patients with treatment-resistant depression (4). Several studies have evaluated the efficacy of bilateral high-frequency (10 Hz) (5,6) and low-frequency (1 Hz) (50) Li-TMS applied to the dorsolateral prefrontal cortex (DLPFC) in patients with depression and insomnia over a 6-week period, totaling 30 sessions. These studies showed improvement in depressive symptoms and sleep quality in adults beginning at session 10 (5) and 15, respectively, as assessed by the Pittsburgh Sleep Quality Index (PSQI) and the Patient Health Questionnaire-9 (PHQ9) (7). The exact mechanism by which Li-TMS improves sleep quality in patients with depression remains unclear. However, evidence indicates that patients who underwent high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) demonstrate improvement in sleep patterns, improvement in sleep stage, positive correlations in motor evoked potential, negative correlations with GABA and BDNF levels, as well as decreased levels of thyroid hormone, adrenocorticotropic hormone, and thyroid-stimulating hormone (5).

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